Method for treating surfaces, and associated bodies and uses

Abstract

In order to achieve novel surface properties, a method is proposed in which, at comparatively low temperatures and under the influence of a pressure within a pressure reactor (19), metal atoms (34) are dissolved out of a carrier body (3) and / or a sacrificial material (27) with the aid of a reactive liquid (11) in order to subsequently regrow the dissolved metal components (48) in the form of microstructures (1) on the surface (2) of the carrier body (3), namely within the liquid phase (22) formed by the reactive liquid (11).

Description

[0001] PC 26 0577 C 24 March 2026

[0002] Methods for the treatment of surfaces and associated bodies and uses

[0003] The invention relates to a method for treating a (particularly metallic) surface of a substrate, the method being especially suitable when the surface is made of aluminum. The substrate whose surface is treated by the method can be a wide variety of technical components (metallic as well as non-metallic), even those with complex three-dimensional geometries. The method aims to create nano- and / or microstructures exhibiting technically usable surface effects on such a complex surface, which may also have been pretreated, for example, by sandblasting. Depending on the process duration, the method can also produce closed functional layers (particularly hard layers) composed of such (crystalline) microstructures / microcrystals.Furthermore, it is possible to use the method to create complex layer systems consisting of several such layers.

[0004] In the case of an aluminum or other metallic surface treated by the method, this surface can be formed directly from a bulk material of the support body. For example, the support body itself can be made of metal / aluminum. However, the support body can also be made of a non-metallic material such as glass. In the latter case, the support body can have an outer metallic coating (particularly in the form of an aluminum layer) that forms the surface to be treated / aluminum surface. It is known that aluminum surfaces exposed to an oxygen-containing atmosphere develop a very thin, few nm layer in a short time. PC 26 0577 C 2 / 29 24 March 2026

[0005] A thick native oxide layer of aluminum oxide forms. In such a case, this aluminum oxide layer then forms the outermost boundary layer of the aluminum surface, as the starting point of the process.

[0006] A method for producing pyramidal titanium nanostructures with bactericidal properties on a titanium surface using a hot vapor phase at temperatures above 160°C is already known from WO 2021 000982 Al. This allows titanium surfaces to be endowed with new properties, which is of particular interest for implants. However, the high thermal stresses are a disadvantage, precluding this method from being used in numerous applications.

[0007] Against this background, the invention aims to provide a further method for modifying surfaces so that they can be used for new technical applications. The method should be designed to be as environmentally friendly as possible and also energy-efficient.

[0008] To solve this problem, the invention provides the features of claim 1 in a method for treating the surface of a support body. In particular, the invention proposes that, to solve the problem in a method of the type described above, nano- and / or microstructures exhibiting surface effects and / or closed functional layers, especially hard layers, are grown from such microstructures in a liquid phase on the surface by means of the method. In particular, a single (more or less closed, especially completely closed) layer can be grown using the method. For this purpose, the invention proposes that the support body be placed in a PC 26 0577 C 3 / 29 24 . March 2026

[0009] The substrate is placed in a pressure reactor and the surface to be treated is (completely) covered with a reactive liquid within the pressure reactor. This liquid, which thus forms the liquid phase, serves as a medium that promotes the diffusion of the dissolved metal components, thereby enabling the most homogeneous possible growth of the crystals at comparatively low temperatures (unlike the aggressive vapor phase used in the process according to WO 2021 000982 Al).

[0010] Subsequently, in a dissolution process A) (within the pressure reactor and within the liquid phase), metal atoms are leached from the support material (e.g., from metallic bulk material of the support material that forms the surface; or from a metallic coating forming the surface, which is supported by the support material) and dissolved in the liquid phase as dissolved metal components. Such dissolved metal components can be, for example, metal ions and / or metal oxides and / or metal hydroxides.

[0011] In addition or as an alternative, such dissolved metal components can also be (especially exclusively) removed from a sacrificial material that is (at least partially) immersed in the reactive liquid (and thus also located within the pressure reactor). Such a sacrificial material can be introduced into the reactive liquid, for example, in the form of a sacrificial body or as a (especially microscopically fine) powder (in the case of a powder, the dissolution process then takes place on many small powder particles, which can be macroscopic or microscopically small). In this case, the sacrificial material provides the majority or even all of the metal atoms that dissolve in the dissolution process A). The use of a sacrificial material can be advantageous, PC 26 0577 C 4 / 29 24 March 2026

[0012] to significantly shorten the process time for forming the desired nanostructures. Furthermore, a much more uniform deposition of nanostructures can often be achieved across the entire (exposed) surface of the substrate.

[0013] The process can dissolve not only base metals such as aluminum in the reactive liquid, but also metallic alloys, such as cobalt-chromium, as used, for example, in medical implants. The material providing the metal atoms can be considered the starting material for the process / structural growth. If the metal atoms are provided, for example, in the form of aluminum atoms from an aluminum support structure, then this bulk material of the support structure constitutes the starting material. However, the starting material can also be a metallic top layer of the support structure and / or a sacrificial material that is provided in the reactor and / or previously applied to the support structure (e.g., by rolling on a thin metal foil or by vapor deposition / sputtering).

[0014] It has now been surprisingly observed that the metal components dissolved in this way can grow in a new morphology on the surface of the support body (re-deposition). As investigations using SEM images have shown, this initially leads to the formation of sponge-like structures, which can be further modified in the course of the process, so that ultimately geometrically regular, in particular cuboid / cuboid-like, structures / crystals can be formed.

[0015] Within the framework of the process, at least a portion of the metal components dissolved in the dissolution process A) are thus formed in a build-up process B) to create the nano-PC 26 0577 C 5 / 29 24 . March 2026

[0016] and / or microstructures are deposited / redeposited on the surface of the substrate. Through this redeposition of metal atoms, the nanostructures and / or microstructures grow continuously in the liquid phase. For example, the build-up process A) can be continued until microcrystals with dimensions > 1 pm have formed. In contrast to electroplating processes, this growth occurs without the influence of an electric field resulting from an externally applied electrical voltage. If the growth is continued further, closed (functional) layers can form from the microcrystals, as mentioned. The process duration determines whether the resulting layer is completely closed or not.

[0017] As mentioned at the outset, the support body can have an outer metallic coating or an outermost metallic layer that forms the surface to be treated. However, it is also conceivable to deposit metal atoms from a separate sacrificial body (which dissolve in process A) onto a non-metallic surface of a non-metallic support body. In this case, the support body does not provide any metal atoms at all.

[0018] The build-up process B) takes place in a pressure reactor under the influence of a controlled temperature T and a controlled pressure p. Here, T can be less than 150°C, particularly less than 120°C or even less than 100°C. The shape of the resulting crystals can be influenced by selecting this process temperature T. For microstructures comprising aluminum, a preferred value range for T is 60°C ± 20°C, particularly preferably 60°C ± 10°C. Below 35°C, however, no layer growth was observed, which is why this represents the lower limit. PC 26 0577 C 6 / 29 24 March 2026

[0019] The pressure p, however, can be less than 1 bar above the atmospheric pressure prevailing in the vicinity of the pressure reactor. The process according to the invention can therefore be understood as a low-temperature (typically < 100°C) and low-pressure (<1 bar) process.

[0020] A further characteristic of the process is that the metal atoms growing on the surface in a new morphology originate at least partially (or even completely – if a separate sacrificial material is omitted) from this original surface of the substrate. In other words, in the process, a metallic top layer of the substrate is locally dissolved in dissolution process A) and then rebuilt in a new morphology at the same location in build-up process B); this could, for example, be a metal oxide layer. The technical effects provided by the new surface are based on the change in its microscopic to nanoscopic morphology. That is, the surface-active effects provided by the new nano / microstructure are not observable on the original surface.

[0021] In the process according to the invention, it was experimentally observed using SEM images that microstructures and nanostructures can grow, in particular simultaneously. Here, microcrystals initially grow on the surface as individual crystals, while grass-like nanostructures can form in the spaces between them. The size of the crystalline microstructures increases continuously with the duration of the process. Above a certain size, the microcrystals grow together and then form more or less closed layers (= functional layer). With sufficient process duration, completely closed layers are formed. The thicknesses of such layers can be in the range of 3-20 pm. PC 26 0577 C 7 / 29 24 March 2026

[0022] During the growth of such a layer, a conversion layer (especially based on an existing metallic layer of the support body) can temporarily form, the morphology of which is gradually changed by crystal growth in the build-up process B).

[0023] With a sufficiently long process time, hard layers consisting of crystalline microstructures grown from the liquid phase using this method can be produced, particularly on aluminium surfaces.

[0024] As mentioned at the outset, the method can be used in particular to produce nano- and / or microstructures on an aluminum surface. The invention thus allows surfaces, especially those made of aluminum, to be refined in such a way that they can be used for new applications because the structures or hard layers produced impart new properties to the surface (e.g., with regard to surface hardness, surface durability, sliding or static friction, wetting properties, anti-adhesion properties, or even bactericidal / biological / chemical effects).

[0025] Redeposition here can be understood as the redeposition of metal atoms (especially aluminum) that were previously dissolved (by exposing metallic material of the support body and / or sacrificial material to the reactive fluid in the pressure reactor). If a support body has a metallic surface

[0026] If a substrate (= starting material) is used, the dissolution and redeposition of the metal atoms can lead to a morphological transformation of the uppermost metallic layer of the substrate. For example, if a substrate with an aluminum or aluminum oxide starter layer is used, PC 26 0577 C 8 / 29 24 . March 2026

[0027] To form the surface to be treated, nanocrystals (with dimensions in the submicrometer range) of aluminum oxide can initially grow on the substrate. These nanocrystals can already form a desired nanostructure and thus achieve the desired surface-active effects. As the build-up process (B) continues, individual nanostructures enlarge to microstructures with dimensions in the range > 1 pm. It has been observed that the structures produced in this way are mechanically more stable than the starting material.

[0028] The dissolution process A, by which at least parts of the metallic starting material are brought into solution, can in particular be designed as a hydrothermal oxidation.

[0029] This process allows for the targeted adjustment of surface-active properties such as wettability, as well as the achievement of biological and chemical effects. Furthermore, the process can also increase the surface hardness of the substrate or enhance corrosion resistance to various substances compared to the untreated surface.

[0030] It can also be speculated that the process could potentially be used to create long-term stable antibacterial surfaces on aluminum bodies or aluminum layers (which, for example, are applied to a different substrate such as glass), since the grown / generated nano / microstructures can also exhibit bactericidal effects depending on their crystal form. This could be of interest, for example, for use in ventilation systems, where aluminum surfaces are frequently used.

[0031] Surfaces treated / finished using the process, PC 26 0577 C 9 / 29 24 March 2026

[0032] Not only can surfaces become more mechanically and / or chemically robust, for example by exhibiting increased corrosion resistance compared to the untreated surface, but the generated nano- and microstructures can also achieve, for example, "anti-fingerprint" effects or purely optical-aesthetic effects on the treated surface. By using masking agents (e.g., protective films or coatings), the structures can also be created locally on specific areas of the substrate's surface.

[0033] With regard to the finishing of aluminum surfaces, the invention proposes in particular the following method variant: A method for treating an aluminum surface of a substrate is proposed, wherein the method grows (at least) a functional layer (this layer can be partially or completely closed, depending on the process duration), in particular (at least) a hard layer, consisting of crystalline microstructures with dimensions greater than 1 pm in a liquid phase on the aluminum surface. For this purpose, the substrate is placed in a pressure reactor and its aluminum surface is covered with ultrapure water in the pressure reactor, which thus forms the liquid phase as the reactive liquid.Furthermore, in a dissolution process A), metal atoms are dissolved from the support material and / or from a sacrificial material immersed in the reactive liquid / pure water and dissolved in the liquid phase as metal components (such as metal ions and / or metal oxides and / or metal hydroxides). In a build-up process B), at least a portion of the metal components dissolved in dissolution process A) are then redeposited onto the aluminum surface of the support material, forming the desired functional layer. PC 26 0577 C 10 / 29 24 March 2026.

[0034] Advantageously, this process can be carried out in an energy-efficient manner at a process temperature T within the pressure reactor during the build-up process B) of less than 140°C. Such a low-temperature process, which does not require aggressive alkalis and acids, is environmentally friendly and can contribute to reducing CO2 emissions. The invention has specifically recognized that, even with ultrapure water, under suitable low-temperature conditions in a pressure reactor, aluminum oxide starter layers can dissolve and subsequently be redeposited / re-grown in the form of microcrystals to produce hard coatings. This allows the treated substrate to be made, for example, more wear-resistant or to prevent corrosion over long periods, even when exposed to aggressive acids.The corrosion resistance in particular is significantly improved with the inventive method, with the low process temperature and the associated comparatively long times for the growth of the microstructures offering advantages in this regard.

[0035] Further possible embodiments, which are also listed in the dependent claims, are now described:

[0036] As a reactive fluid, in addition to ultrapure water, aqueous ammonia, KOH, or NaOH can also be used to form the aforementioned liquid phase (these substances can also be used in combination) in which the nano / microstructures grow on the surface. Unlike, for example, electroplating, this eliminates the need for liquids that are very harmful to the environment. Ultrapure water also acts as an acid under the conditions of the pressure reactor and can thus dissolve metal atoms. For example, this can also dissolve an aluminum oxide layer present at the outermost interface of the substrate (such as that found in the form of an ultrathin PC 26 0577 C 11 / 29 24 March 2026).

[0037] (native oxide layer found on every aluminum body) can be dissolved.

[0038] During most of the build-up process B), the temperature of the liquid phase can preferably be kept below 100°C, which promotes the formation of nano- to microstructures. Preferably, a pressure of < 1 bar can also be maintained within the pressure reactor for most of the build-up process B). However, since the solubility of the respective uppermost material layer (of the support body and / or the sacrificial material / powder, in particular an initially present aluminum oxide starter layer) is temperature-dependent and increases with rising temperature, an elevated temperature (> 100°C) can be advantageously used at the beginning of the process to accelerate the dissolution process A) and thus shorten the overall process duration.

[0039] The surface (more precisely: that part of the total surface of the support body on which the structures are to be grown) remains completely immersed in the reactive liquid / liquid phase during both the dissolution process A) and the build-up process B). A portion of the support body may be in a vapor phase that forms above the liquid phase in the pressure reactor; however, this vapor phase is not crucial for the growth of the structures and does not directly affect the surface, as the surface remains covered by the reactive liquid.

[0040] The redeposition of the metal atoms (which can be dissolved, for example, from a metallic layer previously produced or deposited on the support, such as an aluminum oxide starter layer) occurs in build-up process B), while the support remains exposed to the liquid phase. The dissolution and redeposition can be carried out according to PC 26 0577 C 12 / 29 24 March 2026

[0041] The process control (especially the temporal temperature and pressure profile) is designed as a dynamic overall process in which both processes A) and B) occur simultaneously, but with increasing process duration, a morphological transformation towards the desired structures occurs. The build-up process B) can form (e.g., cuboid) crystals whose edge length can reach the micrometer range, depending on how long the build-up process B) is maintained in the pressure reactor.

[0042] Alternatively, the process can also be designed in such a way that the dissolution process A) is carried out completely as the first process step and the build-up process B) is carried out subsequently, in particular in a separate reactor.

[0043] A starting material from which the metal atoms are dissolved can preferably contain at least one precursor that accelerates the dissolution process A), selected from the following group of materials: silicon, manganese, magnesium, copper, zinc. Several of the aforementioned precursors can also be used in the process. In particular, a bulk material of the support body or the aforementioned sacrificial material can contain and thus provide such a precursor. For example, a thin (e.g., less than 10 pm) layer of A1S112, applied to the support body before it is placed in the pressure reactor, can be used. Here, the silicon accelerates the dissolution of the Al metal atoms from this sacrificial layer in the dissolution process A).

[0044] A preferred embodiment therefore provides that the support body is made of an aluminum-silicon alloy or at least comprises an outer layer of this material. PC 26 0577 C 13 / 29 24 March 2026

[0045] For example, if an aluminum oxide starter layer is exposed to the liquid phase as part of the support body, while a sacrificial body is in the liquid phase that can release one or more of the elements silicon, manganese, magnesium, copper or zinc into the liquid phase, this can also accelerate / facilitate the dissolution process.

[0046] As already mentioned, if the build-up process B) lasts long enough, crystalline microcrystals with dimensions > 1 pm can be formed.

[0047] One embodiment provides that the substrate (which can be, in particular, an aluminum substrate) has an aluminum oxide start layer as a sacrificial layer, wherein this start layer preferably has a start layer thickness of at least 20 nm, particularly 20–2000 nm. This start layer can be a native oxide layer. If greater start layer thicknesses are required, it can also be artificially pre-generated / built up. For example, the aluminum oxide start layer can be deposited from a gas phase onto the substrate (in particular onto a native oxide layer of the substrate) or it can be built up in situ from an aluminum material / aluminum bulk material of the substrate, preferably by electrochemical anodizing.

[0048] If such an aluminum oxide starter layer is exposed to the liquid phase under hydrothermal oxidation conditions during build-up process B), it is preferred that a process temperature of T < 100 °C, in particular a temperature of 55–85 °C, and / or a pressure of < 1 bar prevail within the pressure reactor. In such a case, the described dynamic process of simultaneous layer dissolution and redeposition of the metal atoms / aluminum oxide can be carried out using a PC 26 0577 C 14 / 29 24 March 2026

[0049] This can be achieved through hydrothermal oxidation. In particular, this process makes it possible to create a closed, crystalline, and redeposited aluminum oxide end layer on the substrate.

[0050] It has already been mentioned that the carrier body can be made entirely of aluminum or an aluminum alloy (so that this material can provide Al atoms) or can only have an outer layer of aluminum or an aluminum alloy, which outer layer is then treated with the process.

[0051] One embodiment provides that the support body consists of a metallic alloy, in particular an aluminum alloy. For the reasons explained, it is advantageous if the alloy / aluminum alloy is doped with one or more of the following elements: silicon, manganese, magnesium, copper, or zinc. To achieve a sufficient effect on the process, the total doping concentration should be at least 0.5%.

[0052] The method allows the formation of nano- to microstructures with a (respective) height H, which – measured normal to the surface of the support material (this can be, for example, the aforementioned aluminum surface) – can range from 20 to 5000 nm. For example, the build-up process B) can be applied until cuboid nanocrystals or cuboid microcrystals (4), preferably with edge lengths > 2 pm, are formed. The morphology of these structures can be controlled by selecting the process time and the process temperature.

[0053] Another embodiment, however, provides that to achieve a surface-active effect, a PC 26 0577 C 15 / 29 24 . March 2026

[0054] The total process time is shortened / chosen in such a way that only nanostructures with an edge length of at most 300 nm are formed, but no microstructures.

[0055] The nano- and / or microstructures produced in the process are fundamentally mechanically stable and can, in particular, be mechanically more stable than a material of the support body.

[0056] To solve the problem, a support body is of course also proposed which carries a nano- / microstructure 1 that was produced using a method as described above.

[0057] Finally, the invention also proposes the use of nano / microstructures produced according to the invention (these can, as explained, be realized in particular in the form of an artificially grown aluminum oxide layer of microcrystals) for certain purposes, namely (i) as an outer hard layer of the substrate (this can be advantageously used, for example, to increase surface hardness and / or fatigue strength of the substrate); or (ii) to reduce sliding friction; or (iii) as an outer functional / surface-active layer, in particular to modify wetting properties and / or to achieve an anti-adhesive effect and / or an optical effect and / or a bactericidal effect and / or a chemical effect and / or a biological effect. Finally, microstructures produced by the method, in particular hard layers, can also be used (iv) as an abrasive (e.g.,(if small grains are treated as carrier bodies using the method) .PC 26 0577 C 16 / 29 24 . March 2026.

[0058] The invention will now be described in more detail with reference to exemplary embodiments, but is not limited to these embodiments. Further embodiments of the invention can be derived from the following description of a preferred embodiment in conjunction with the general description, the claims, and the drawings.

[0059] It shows:

[0060] Fig. 1 shows a schematic view of a first method according to the invention.

[0061] Fig. 2 shows a schematic view of a second method according to the invention.

[0062] Fig. 3 shows the growth of microcrystals on an aluminum substrate bearing an aluminum oxide starter layer.

[0063] Fig. 4 shows the continuous increase in the size of micro-crystals as they grow until a closed new layer is formed.

[0064] Fig. 5 Details of the dissolution and build-up process that are carried out in the method according to the invention,

[0065] Fig. 6 shows a schematic view of a pressure reactor during individual phases of a process according to the invention, and

[0066] Fig. 7 shows an analogous view to that of Fig. 6, but using a separate sacrificial body.

[0067] Figure 1 illustrates individual steps of a method according to the invention, by which a surface 2 of a carrier body 3 can be refined. As in the example of PC 26 0577 C 17 / 29 24 March 2026

[0068] As illustrated in Figure 6, the support body 3 is first placed in a pressure reactor 19, and the surface 2 to be treated (this can also be only a portion of the entire surface of the support body 3) is completely covered with a reactive liquid 11, for example, ultrapure water. The temperature is then increased so that a vapor atmosphere 21 forms inside the reactor, and consequently, the pressure p inside the reactor 19 also increases. Under these conditions, the reactive liquid 11 begins to locally dissolve the surface 2 of the support body 3, whereby during this dissolution process A) (which is designated by reference numeral 17 in the diagram of Figures 1 and 2), metal atoms 34 from the support body 3 dissolve into the reactive liquid 11.As illustrated in Figure 5b, the metal atoms 34 can, for example, dissolve in the liquid phase 22 formed by the reactive liquid 11 in the form of metal ions or metal oxides 37 or metal hydroxides 43.

[0069] As illustrated in Figure 6b, a dynamic process 23 can subsequently establish itself on the surface 2 of the support body 3, in which metal atoms 34 continue to dissolve, but also – within the framework of a build-up process B (= step 18 in Figures 1 and 2) – some of the dissolved metal components 48 are redeposited on the surface 2, which can be described as redeposition. Due to the diffusion promoted by the liquid phase 22, the dissolved metal components 48 are deposited at energetically favorable positions, so that nanostructures 1 can form starting from individual crystallization nuclei 46 (as illustrated in Figure 4a). These nanostructures 1 grow with increasing process duration into microscopically large structures, in particular into microcrystals 4, as illustrated in Figure 4b). If the growth process B)PC 26 0577 C 18 / 29 24 . March 2026

[0070] Continued, the resulting microcrystals 4 grow together until a closed functional layer 35 has formed (compare figure 4c).

[0071] In the example shown in Figure 2, the carrier body 3 is first subjected to a pretreatment 15 before being introduced into the reactive liquid 11 to initiate the dissolution process A) 17. After a sufficient quantity of metal components 48 has been dissolved (particularly at elevated temperature), the carrier body 3, along with the reactive liquid 11, can be removed from the first pressure reactor 19a and introduced into a second pressure reactor 19b. This second pressure reactor 19b also contains the reactive liquid 11 and a sufficient quantity of dissolved metal components, allowing the build-up process B to proceed within this second pressure reactor 19b, as illustrated in Figure 2, at a lower temperature T. Finally, the carrier body 3 treated in this way can undergo a post-treatment 16.

[0072] Figure 3 illustrates a possible application example of a method according to the invention on an aluminum body 3, which has an aluminum oxide starter layer 8 with a starter layer thickness 9 on its surface 2. This starter layer 8 may, for example, have been artificially built up beforehand to provide a sufficient amount of sacrificial material 27 for the subsequent dissolution process A) according to the invention. If such a carrier body 3 is subjected to a method according to the invention, the aluminum oxide starter layer 8 partially dissolves, with aluminum atoms 34 from the layer 8 dissolving into the reactive liquid 11. Depending on the duration and extent of the dissolution process A), aluminum atoms from the uppermost material layer 10 of PC 26 0577 C 19 / 29 24 . March 2026

[0073] Aluminum support body 3 go into solution.

[0074] During the build-up process B) 18, which, as shown in Figure 1, can also occur simultaneously with the dissolution process A) 17, microcrystals 4 grow from these dissolved metal components 48, initially forming isolated crystals 47, as illustrated in Figure 3. As shown in Figure 4, with increasing duration of the build-up process B), completely closed functional layers 48 can be obtained, which are composed of crystalline metal oxide crystals 44.

[0075] As illustrated in Figure 4, the size of the resulting structures 1 increases continuously during the build-up process B), so that, given a sufficiently long process duration, the resulting, still isolated crystals 47 can already have lengths in the range of a few micrometers at the end of this growth process. The nano- to micro-structures 1 produced in this way are characterized by special properties: These structures 1 are completely stable, exhibit surface-active effects, and can also generate optical interference colors. In addition, the structures produced by the method according to the invention are

[0076] Layers mechanically more stable than the original material 33 of the carrier body 3.

[0077] In the example of Figure 5, it can be seen that the original surface 2 of the support body 3 does indeed have metal atoms 34, but no morphology that would produce a surface-active effect. However, the growth process triggered by the method according to the invention changes the morphology of the at least partially dissolved uppermost material layer 10. Here, a new functional layer 35 is built up from the original material 33 of the support body 3, which then forms the PC 26 0577 C 20 / 29 24 . March 2026

[0078] exhibits desired altered surface properties (for example, higher corrosion resistance due to an altered crystal lattice 40).

[0079] In the example of Figure 6, a functional metal oxide layer 5, 35 was produced inside the pressure reactor 19 on the support body 3 over its entire surface 2 immersed in the liquid 11.

[0080] In the example of Figure 7, a separate sacrificial material 27 in the form of a macroscopic sacrificial body is located within the reactive liquid 11, along with the support body 3. Therefore, with a corresponding increase in temperature during the dissolution process A), metal atoms 34 are also released from the sacrificial material 27.

[0081] These metal atoms 34, which have dissolved from the sacrificial material 27, are redeposited on the sacrificial body 27 as an oxide layer 32, but also on the surface 2 of the support body 3, so that a desired functional metal oxide layer 5 with new surface properties is obtained there. Such a sacrificial material 27 could, for example, also be added to the reactive liquid 11 in the pressure reactor 19 in the form of a powder.

[0082] If a so-called precursor, in particular silicon, manganese, magnesium, copper or zinc, is added to reactor 19 (this can be done, for example, by the carrier body already having the precursor, as is the case with a carrier body made of an aluminum-silicon alloy, or by the precursor being provided in the reactor in the form of a sacrificial material), the dissolution process A) can be accelerated.

[0083] In summary, a method is proposed to achieve new surface properties, in which, for comparison PC 26 0577 C 21 / 29 24 . March 2026

[0084] At low temperatures and under the influence of pressure within a pressure reactor 19, metal atoms 34 from a support body 3 and / or from a sacrificial material 27 are dissolved using a reactive liquid 11 in order to subsequently allow these dissolved metal components 48 to grow anew in the form of microstructures 1 on the surface 2 of the support body 3, again within the liquid phase 22 which is formed by the reactive liquid 11 (compare Figure 7). PC 26 0577 C 22 / 29 24 March 2026

[0085] Reference symbol list

[0086] 1 Nano- / microstructure (grown on 2)

[0087] 2 Surface area (out of 3)

[0088] 3 carrier bodies

[0089] 4 microcrystals (out of 1)

[0090] 5 functional metal oxide layer (= possible result of the process; in particular aluminum oxide layer)

[0091] 6 nanocrystals (of 1; especially in the form of nano-grass) 7 layer system (comprising 1 and 5)

[0092] 8 Aluminum oxide start layer (can form the starting point of the process)

[0093] 9 Starting layer thickness (= thickness of 8 after completion of preprocessing of 3)

[0094] 10 uppermost material layer (of 3, after complete production of 8)

[0095] 11 reactive fluid

[0096] 12 Aluminum surface (may have a native aluminum oxide layer)

[0097] 13. Process start

[0098] 14 End of process

[0099] 15 Pretreatment

[0100] 16 Aftercare

[0101] 17 Dissolution process A)

[0102] 18. Construction process B)

[0103] 19 Pressure reactor

[0104] 20 Reactor inner wall

[0105] 21 steam atmosphere (within 19)

[0106] 22 liquid phase

[0107] 23 dynamic process (from 17 and 18)

[0108] 24 concentration out of 48 at process start

[0109] 25 concentration of 48 during 23

[0110] 26 Concentration of 48 at the end of the process

[0111] 27 Sacrificial material (especially in the form of a sacrificial body) 28 Surface (of 27) PC 26 0577 C 23 / 29 24 March 2026

[0112] 29 71b see ide before gang

[0113] 30 Dissolution and deposition process on the surface material of the carrier body 3

[0114] 31 Dissolution and separation process at 27

[0115] 32 resulting oxide layer at 27

[0116] 33 Material (= Bulk material of 3)

[0117] 34 metal atoms

[0118] 35 functional layers

[0119] 36 Oxygen (in the form of O2, O- or OH- ions)

[0120] 37 Metal oxide

[0121] 38 mean layer thickness of 5 / mean height of crystals 4 of 5

[0122] 39 mean lateral size of the crystals 4 out of 5

[0123] 40 crystal lattices (structure of 5)

[0124] 41 Boundary layer (between 33 and 5)

[0125] 42 structures of 33

[0126] 43 Metal hydroxide

[0127] 44 Metal oxide crystal trap

[0128] 45 fused crystals

[0129] 46 initial crystallization nuclei

[0130] 47 growing, still isolated crystals

[0131] 48 metal components (eliminated from 33 and / or 27;

[0132] solved in 11 / 22, e.g. in the form of 37, 43)

Claims

PC 26 0577 C 24 / 29 24 March 2026 Claims 1. Method for treating a surface (2 ), in particular an aluminium surface ( 12 ), a support body (3) , - wherein the method applies to the surface ( 2 ) - Nano- and / or microstructures exhibiting surface effects ( 1 ) and / or - at least one functional layer, in particular a hard layer, made of microstructures ( 1 ) in a liquid phase ( 22 ) and where: - the carrier body ( 3 ) is placed in a pressure reactor ( 19 ) and its surface ( 2 ) in the pressure reactor ( 19 ) is covered with a reactive liquid ( 11 ) which forms the liquid phase ( 22 ); - in a dissolution process A) ( 17 ) metal atoms ( 34 ) - from the carrier body ( 3 ) and / or - from a sacrificial material immersed in the reactive fluid ( 11 ) ( 27 ) dissolved and dissolved in the liquid phase (22) in the form of dissolved metal components (48), such as metal ions and / or metal oxides (37) and / or metal hydroxides (43); and - in a build-up process B ) ( 18 ) at least a part of the metal components ( 48 ) dissolved in the dissolution process A) ( 17 ) are redeposited on the surface ( 2 ) of the support body ( 3 ) by forming the desired nano- and / or microstructures ( 1 ) and / or closed layers .

2. Method according to claim 1, wherein the sacrificial material (27) is applied to the carrier body (3) before the carrier body (3) is introduced into the pressure reactor, in particular by rolling or vapor deposition, and / or - wherein the method produces a layer system ( 7 ) herge-PC 26 0577 C 25 / 29 24 March 2026 is represented, which includes the microstructures ( 1 ) and the functional layer (5, 35 ).

3. Method according to any of the preceding claims, wherein the sacrificial material (27) is provided in the form of a powder which is mixed with the reactive liquid (11).

4. Method according to any of the preceding claims, wherein the reactive liquid comprises ultrapure water and / or aqueous ammonia and / or KOH and / or NaOH.

5. Method according to one of the preceding claims, wherein a process temperature T within the pressure reactor ( 19) during the build-up process B) is less than 140°C, in particular less than 100°C, and / or - wherein a process pressure p inside the pressure reactor ( 19) during the build-up process B) is less than 1 bar above atmospheric pressure .

6. Method according to one of the preceding claims, wherein a starting material from which the metal atoms (34) are dissolved also contains at least one precursor accelerating the dissolution process A) which is selected from the following group of materials: silicon, manganese, magnesium, copper, zinc.

7. A method according to the preceding claim, wherein at least one precursor - is provided from / the victim material (27) and / or - that an aluminium material (33) of the carrier body (3) contains at least one precursor and thus makes it available for the process .

8. Method according to one of the preceding claims, wherein during the growth of the microstructure (1) crystalline micro-PC 26 0577 C 26 / 29 24 March 2026 Crystals (44, 45) with dimensions > 1 pm are formed.

9. Method according to any of the preceding claims, wherein the dissolution process A) and the build-up process B) are designed as a dynamic process (23) such that both processes A) and B) run simultaneously or - wherein the build-up process B) is only carried out after the complete dissolution process A) has been completed, in particular in a separate pressure reactor.

10. Method according to one of the preceding claims, wherein the carrier body (3) comprises an aluminium oxide starter layer (8) as a sacrificial layer (27), - preferably with a starting layer thickness ( 9) of at least 20 nm, in particular of 20-2000 nm.

11. Method according to any of the preceding claims, - wherein the support body (3) is made entirely of aluminium or an aluminium alloy or - wherein the carrier body (3) has only an outer layer of aluminium or an aluminium alloy, which outer layer is treated by the method.

12. Method according to any of the preceding claims, wherein the nano- / microstructures ( 1 ) have a height H, measured normal to the surface of the support body (3) , of 20-5000 nm.

13. Method according to any of the preceding claims, wherein the method, in particular the assembly process B), is applied until - geometrically regular, e.g. cuboid, nanocrystals ( 6) or - geometrically regular, e.g. cuboid, microcrystals (4 ) , preferably with edge lengths > 2 pm, are designed or PC 26 0577 C 27 / 29 24 March 2026 - wherein, to achieve a surface-active effect, a total process time is chosen such that nanostructures ( 1 ) with an edge length of at most 300 nm are formed .

14. Method according to one of the preceding claims, wherein the support body (3) consists of a metallic alloy, in particular an aluminum alloy, - preferably wherein the alloy / the aluminium alloy is doped with one or more of the following elements: silicon, manganese, magnesium, copper or zinc, - in particular where the concentration of the total doping is at least 0.5%.

15. Method according to any of the preceding claims, wherein the aluminium oxide start layer ( 8 ) is exposed to the liquid phase (22 ) while a sacrificial body is located in the liquid phase (22 ) which can release one or more of the elements silicon, manganese, magnesium, copper or zinc into the liquid phase (22 ).

16. Method according to any of the preceding claims, wherein the aluminium oxide starter layer ( 8 ) of the liquid phase (22 ) is exposed to hydrothermal oxidation conditions, - preferably wherein a temperature < 100 °C, in particular a temperature of 55-85 °C, and / or a pressure of < 1 bar prevails within the pressure reactor ( 19 ).

17. Carrier body (3) carrying a nano / microstructure (1), in particular in the form of an aluminum oxide layer (5) as a functional layer (5, 35) produced by a method according to one of the preceding claims, wherein the nano / microstructure (1) is mechanically stable. PC 26 0577 C 28 / 29 24 March 2026 and / or at least a surface-active effect, e.g. - an optical and / or - an anti-adhesive effect and / or - a bactericidal effect shows .

18. Use of a nano / microstructure (1), in particular an artificially grown aluminium oxide layer (5) of microcrystals (4), which was produced as a functional layer (5, 35) on a substrate (3) by a method according to any one of claims 1 to 16, as an outer hard layer of the substrate (3), preferably to - a surface hardness and / or - durability to increase the carrier body (3) or - to reduce sliding friction, or as - an outer surface-active layer (35) , in particular around - to change wetting properties and / or - an anti-adhesive effect and / or - an optical effect and / or - a bactericidal effect and / or - a chemical effect and / or - a biological effect to achieve or as an abrasive.

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