DE102007027628B3 - Method of introducing nanoparticles into anodized aluminum surface - Google Patents

Abstract

The invention relates to a method for treating anodized aluminum surface (11) with pores (13), wherein nanoparticles (14) are introduced into these pores. According to the invention, it is provided that the nanoparticles are dispersed in a liquid dispersion medium prior to introduction and subjected to after-treatment after introduction. In this case, an energy is introduced into the pores (13), which leads to a reaction of the nanoparticles (14) with further constituents of the dispersion, so that at least their surface is converted. In this way, for example, nanoparticles (14) of silicates, in particular borosilicate, which are outstandingly adherent in the pores (13) can be produced, these nanoparticles for example serving to receive a catalyst material in the pores.

Description

The The invention relates to a method of treating an anodized oxide Aluminum surface in which open pores are formed, wherein the treating involves introducing nanoparticles into the pores includes.

A method of the type specified is in the DE 10 2005 033 118 A1 described. Thereafter, a catalyst system for an internal combustion engine may be created by, for example, making the surface of the piston of aluminum. The surface of the piston facing the combustion chamber is anodized so that pores are formed in the surface. Nanoparticles, which have a catalytic effect with respect to the combustion process taking place in the internal combustion engine, can already be introduced into these pores during the anodization.

Furthermore, Abstract 2006-300175 describes WPIDS of the application CN 169 89 98 A in that a lubricant of nanoparticles can be introduced into pores of anodized aluminum. For this purpose, an aqueous dispersion of the lubricant is prepared, wherein the water evaporates by a subsequent heat treatment and the lubricant is fixed in the pores in this way.

Last it is from the EP 1 580 305 A2 It is known to introduce metal particles into the anodically produced pores of an aluminum surface by first producing a liquid dispersion therewith, this dispersion then being introduced into the pores and the dispersant (liquid) being removed from the pores by a drying step.

Furthermore, it is from the US 2003/0098240 A1 It is known that aluminum surfaces can be given a certain color by first being anodically oxidized, in which case pores are formed. In these pores, a metal can be deposited by means of a further electrolytic process, which produces a certain color.

The The object of the invention is to provide a method for treating a to indicate anodized aluminum surface, with nanoparticles in the pores of the aluminum surface can be deposited, the extended functional range of the aluminum layer allow.

These The object is achieved by the method mentioned in the present invention solved that the nanoparticles before placing in the Pores are dispersed in a liquid dispersant and after the introduction into the pores, an aftertreatment of the surface occurs under an energy input, which is a chemical reaction the nanoparticles with other components of the dispersion causes, at least chemically to the surface of the nanoparticles change. Of course it is also possible to completely transform the nanoparticles.

By an inventively occurring in the pores reaction The nanoparticles can be advantageous on the one hand the Improve adhesion of nanoparticles in the pores. On the other hand It's possible to make nanoparticles a bigger one To store variety in the pores. For example, nanoparticles can be used into the pores, with which the production of a liquid Dispersion difficulties. It can be nanoparticles be used, which can be dispersed more easily and the as Reaktionsedukt for those to be produced in the pores Nanoparticles can be used.

Farther is also a partial transformation of nanoparticles in the pores possible so that nanoparticles can be generated in the pores, the surface of which shares both the Reaktionseduktes and also has the reaction product.

According to one advantageous embodiment of the invention is provided that as Nanoparticles Aluminum oxide and / or zirconium oxide and / or silicon oxide are added and in the dispersant silica and / or boric acid, wherein in the after-treatment aluminum silicate and / or zirconium silicate and / or borosilicate in the pores getting produced. This can be depending on the mixture of liquid Dispersion silicates with different proportions of aluminum, Manufacture zirconium and borosilicate, the silicates excellent adhere to the walls of the pores. On the other hand, the Silicate nanoparticles their surface also advantageous for adhesion other substances available, which are also to these Adhere well.

Especially It is advantageous if, in a subsequent step, catalyst material is introduced into the pores, which adhere to those in the pores attached silicates attached. The silicates present in the pores be in this variant of the invention, so to speak, only as Primer used, with most catalyst materials outstanding adhere to the silicates. This advantageously creates a substantial Freedom of design with regard to the choice of catalyst materials, so that anodized aluminum surfaces for the various reactions as a catalyst surface available can be made.

It is also advantageous that before the post-treatment, a drying step takes place in which the Dispersants at least partially evaporated. This is advantageous in cases where the dispersant itself is not involved in film formation. An evaporation of the dispersant advantageously leads to a densification of the layers, so that the reactants can react better with one another in the subsequent aftertreatment. In addition, the evaporation of the dispersant already improves the adhesion of the nanoparticles as well as the reactants for the nanoparticles in the pores.

Further details of the invention are described below with reference to the drawing. The 1 schematically shows a section through an anodized aluminum surface, in whose pores nanoparticles are incorporated, this surface was prepared according to an embodiment of the method according to the invention.

A surface 11 is through an aluminum substrate 12 formed, wherein by anodic oxidation pores 13 in the surface 11 of the substrate 12 were manufactured. At this time, the aluminum substrate becomes alumina 12a converted, wherein the resulting pores are arranged relatively regularly. In these pores 13 are nanoparticles by means of the method according to the invention 14 have been introduced, these are shown in part in section. Here it becomes clear that the nanoparticles 14 from a core 15 exist, which has remained as a reaction educt, wherein the shell 16 the reaction product is a post-treatment of the nanoparticles carried out in the process according to the invention.

The inventive method can, for example with the following steps.

First, the surface of the aluminum substrate 12 pretreated. This can be done by grinding, brushing, polishing or chemical matting.

In a next step, the anodic oxidation of the aluminum or aluminum alloy is carried out. This treatment is also referred to as anodizing. It is carried out in acidic media such as sulfuric acid, phosphoric acid, oxalic acid, methanesulfonic acid or mixtures of the acids mentioned. Furthermore, a DC or AC voltage is applied, wherein the aluminum substrate 12 is connected as an anode. Depending on the process conditions (choice of acid, concentration, temperature, voltage, treatment time), this process step results in pore formation whose size can be in the nanometer or micrometer range.

Subsequently is a suspension of the nanoparticles and a dispersant produced. As nanoparticles, preference is given to mixtures of zirconium oxide, Alumina or silica used. Furthermore you can but also boron nitride, titanium nitride, silicon carbide, titanium oxide and Zinc oxide are used. It can also be made up of nanoparticles Silver may be added, their surface in addition partially occupied with palladium (these particles produce a germicidal effect and will be involved in further reactions not involved to obtain their surface).

When Dispersants are preferably used liquid alcohols. The alcohol can be in monovalent form (eg, ethanol, methanol, n-propanol, n-butanol etc.) or in polyvalent form (eg, glycol or glycerin). Water may also be added to the dispersant. Farther the dispersion contains silica and / or boric acid in liquid or crystalline form.

By modifying the composition of the dispersing agent, the viscosity of the dispersion can be adjusted. Depending on the viscosity, the dispersion is applied to the surface 11 by dipping, spinning, spraying, knife coating, brushing or rubbing, wherein in the event that an attachment of the nanoparticles should take place only in the pores, the dispersion is removed from the surface before further treatment, so that only those in the pores penetrated dispersion remains. Alternatively, of course, a part of the dispersion may remain on the surface, so that the surface receives a coating.

additionally to the nanoparticles is also a staining of the surface possible with dyes based on oxide or silicate (for example Spinels, garnets, corundums, cassiterites, rutiles, periderites and Phenancite).

After an optional drying step, for example, by heating the substrate 12 can be supported, the post-treatment is carried out by a thermal sintering treatment, in which the substrate is heated to the temperature required for the reaction of the nanoparticles. During treatment, the nanoparticles are converted to silicates. Depending on the treatment time, a silicate shell is initially formed on the nanoparticles, which are completely converted as the treatment time progresses.

Optionally, a further aftertreatment step for compacting the pores is possible. The surface is treated with water or steam at 80 to 100 ° C, with additives such as an ammonium acetate solution can be added. To Next, in this treatment, a reaction between the alumina and the water takes place on the layer surface and in the pores. This produces the water-rich bayerite. This slowly changes with increasing temperature in the stable crystalline boehmite. In this process, the water absorption leads to an increase in volume, which leads to a narrowing of the pores. Here, the nanoparticles are incorporated into the thickening layer of boehmite, whereby their adhesion is improved.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 102005033118 A1 [0002]
• - CN 1698998A [0003]
• - EP 1580305 A2 [0004]
• US 2003/0098240 A1 [0005]

Claims (4)

Process for treating anodized aluminum surface ( 11 ), in the open pores ( 13 ), the treating comprising introducing nanoparticles ( 14 ) in the pores ( 13 ), characterized in that the nanoparticles ( 14 ) before introduction into the pores ( 13 ) are dispersed in a liquid dispersion medium and after introduction into the pores ( 13 ) a post-treatment of the surface ( 11 ) is carried out under an energy input that causes a chemical reaction of the nanoparticles ( 14 ) with further constituents of the dispersion in order to at least the surface of the nanoparticles ( 14 ) chemically change. Process according to claim 1, characterized in that as nanoparticles ( 14 ) Aluminum oxide and / or zirconium oxide and / or silicon oxide are added and in the dispersant silica and / or boric acid are contained, wherein during the post-treatment in the pores ( 13 ) Aluminum silicate and / or zirconium silicate and / or borosilicate. A method according to claim 2, characterized in that in a subsequent step, a catalyst material in the pores ( 13 ) is introduced, which attaches to the silicates present in the pores. Method according to one of the preceding claims, characterized in that before the post-treatment a drying step takes place, in which the dispersant at least partially evaporates.