Dispersion electrolyte and chemical bath for nickel and nickel alloy layers containing particles

Abstract

The invention relates, inter alia, to a dispersion electrolyte for the electroplating of particle-containing nickel or nickel alloy layers. The dispersion electrolyte comprises 2 to 200 g / L nickel ions, a total of 1 to 200 g / L of at least one type of particle, selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof, an anionic and / or nonionic dispersant, and water. For a nickel alloy, the dispersion electrolyte contains ions of at least one further metal, selected from transition metals, noble metals, and combinations thereof, in a total concentration of up to 40 g / L, and / or at least one non-metal compound, selected from phosphorus compounds, sulfur compounds, selenium compounds, tellurium compounds, carbon compounds, and combinations thereof, in a total concentration of up to 50 g / L. The pH value is 2.0 to 7.0.The dispersion electrolyte can be used to electroplat a layer of nickel or nickel alloy containing particles onto a metallic or metallized substrate.

Description

Technical field of the invention

[0001] The present invention relates to a

[0002] Dispersion electrolytes for the galvanic deposition of particle-containing nickel or nickel alloy layers, a bath for the electroless deposition of particle-containing nickel or nickel alloy layers, a process for the galvanic or electroless coating of a substrate with a particle-containing nickel or nickel alloy layer, a coated substrate with a particle-containing nickel or nickel alloy layer, and an electrochemical cell comprising the coated substrate. Technical background

[0003] For many electronic applications, it is desirable to partially or completely replace precious metals with more cost-effective non-precious metals. In addition to good electrical properties, corrosion resistance is also desirable to achieve long-lasting and thus sustainable electronic components, such as contacts or electrodes. However, many non-precious metals and their alloys exhibit insufficient corrosion resistance, for example, to aqueous alkaline media. Therefore, there is a need to provide electronic components with a corrosion-resistant protective layer.

[0004] For applications in aqueous alkaline media, for example, coatings made of nickel or a nickel alloy can be used. These can be deposited galvanically from an electrolyte or electrolessly, i.e., chemically, from a bath. Such nickel and alloy coatings can therefore serve as a cost-effective replacement for precious metals. However, they often have inferior electrical properties compared to precious metals. This can manifest itself, for example, in increased contact resistance compared to other metals. Furthermore, overvoltages can be observed during electrochemical reactions in aqueous media, especially in aqueous alkaline media, which are often caused by kinetic inhibition of a reaction.It would therefore be desirable to develop coatings that provide good corrosion protection while simultaneously improving electrical properties, particularly reducing overvoltage in aqueous alkaline media. Furthermore, compositions and processes are needed that allow these coatings to be produced economically. Summary of the invention

[0005] An object of the present invention is therefore to provide an electrolyte for the electrodeposition and a bath for the electroless deposition of nickel or nickel alloy layers that are corrosion-resistant in the alkaline range and capable of reducing overpotential for electrochemical reactions in aqueous alkaline media. Further objects are to provide methods for coating substrates with such a nickel or nickel alloy layer using the electrolyte or the bath for electroless deposition, the coated substrate, and applications thereof.

[0006] These objects are achieved by the dispersion electrolyte for the electroplating of particle-containing nickel or nickel alloy layers, the bath for the electroless deposition of particle-containing nickel or nickel alloy layers, the method for electroplating or electroless coating a substrate with a particle-containing nickel or nickel alloy layer using the dispersion electrolyte or the bath, the coated substrate, and an electrochemical cell comprising the coated substrate, according to the independent claims. Optional and preferred embodiments are specified below and in the dependent claims. Short description of the characters They show:

[0007] Fig. 1A scanning electron microscope image of the particle-containing layer of Example 1 Fig. 2A scanning electron microscope image of the particle-containing layer of Example 2 Fig. 3A scanning electron microscope image of the particle-containing layer of Example 3 Fig. 4A scanning electron microscope image of the layer of Comparative Example 1 Fig. 5A) Light microscope image and B) Scanning electron microscope image of the cross-section of Example 2 Fig. 6A) Light microscope image and B) Scanning electron microscope image of the cross-section of Example 3 Fig. 7A light microscope image of the cross-section of Comparative Example 1 Fig. 8A scanning electron microscope image of the particle-containing layer of Example 4 Fig. 9A scanning electron microscope image of the particle-containing layer of Example 5 Fig. 10A scanning electron microscope image of the particle-containing layer of Example 6 Fig.11A) Light microscope image and B) scanning electron microscope image of the cross-section of Example 5 Fig. 12A) Light microscope image and B) scanning electron microscope image of the cross-section of Example 6 Fig. 13A scanning electron microscope image of the particle-containing layer of Example 7 Fig. 14A scanning electron microscope image of the particle-containing layer of Example 8 Fig. 15A scanning electron microscope image of the particle-containing layer of Example 9 Fig. 16A) Light microscope image and B) scanning electron microscope image of the cross-section of Example 8 Fig. 17A) Light microscope image and B) scanning electron microscope image of the cross-section of Example 9 . Detailed description of the invention

[0008] The present invention provides a

[0009] Dispersion electrolytes for the electrodeposition of particle-containing nickel or particle-containing nickel alloy coatings. The dispersion electrolyte comprises: Nickel ions in a concentration of 2 to 200 g / L; at least one type of particle selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof, in a total concentration of 1 to 200 g / L; at least one dispersant selected from anionic dispersants, non-ionic dispersants, and combinations thereof; optionally ions of at least one further metal selected from transition metals, noble metals, and combinations thereof, in a total concentration of up to 40 g / L; optionally at least one non-metal compound other than the dispersant and selected from phosphorus compounds, sulfur compounds, selenium compounds, tellurium compounds, carbon compounds, and combinations thereof, in a total concentration of up to 50 g / L; and water;

[0010] The dispersion electrolyte has a pH value of 2.0 to 7.0. The dispersion electrolyte is also referred to as "electrolyte" in the following.

[0011] The inventors have surprisingly found that, with the dispersion electrolyte according to the invention, it is possible to electrodeposit the uncharged particles together with a nickel layer or a nickel alloy layer, thus forming a particle-containing nickel or nickel alloy layer. The deposited nickel or nickel alloy layer therefore contains, in addition to nickel or nickel alloy, particles of one or more inorganic piezoelectric materials and / or one or more electrically conductive ceramic materials. The deposited nickel alloy typically has a high nickel content of at least 65 wt. %, preferably at least 75 wt. %, more preferably at least 85 wt. %, even more preferably at least 90 wt. %, based on the alloy. The particles are not considered part of the nickel alloy.

[0012] A nickel alloy is electrodeposited when, in addition to nickel ions, ions of another metal, selected from transition and noble metals, which are electrodeposited together with nickel, and / or non-metal compounds that can be decomposed during electrodeposition and serve as precursor compounds for the incorporation of the corresponding non-metal atoms (P, S, Se, Te, and / or C) into the alloy, are present in the dispersion electrolyte. The other metals are different from nickel. The non-metal compounds are different from the dispersant.

[0013] Furthermore, it was surprisingly found that, compared to corresponding nickel or nickel alloy layers without the particles, the overpotential for electrochemical reactions at the interface in aqueous media, especially in aqueous alkaline media, can be reduced with the particles made of an inorganic piezoelectric or electrically conductive ceramic material. Due to the lower overpotential, less current is required for the same electrochemical reaction, thus improving the reaction's economic efficiency.

[0014] The electrolyte enables the particle-containing nickel or nickel alloy layer to be galvanically deposited on a metallic or metallized substrate. The process described below can be used for this purpose, enabling deposition over a wide temperature and current density range. During deposition, the particles are at least partially arranged on the surface of the particle-containing nickel or nickel alloy layer, thus forming part of the surface. The particle-containing nickel or nickel alloy layer is typically created as a final layer, i.e., the outermost layer, for example, as a single layer or part of a layer system, on a substrate.

[0015] Furthermore, it was surprisingly found that the particle-containing nickel or nickel alloy layer, despite the particles, which are basically foreign bodies in the nickel or nickel alloy layer, has good corrosion resistance in the weakly acidic and especially in the alkaline range, which is comparable to the corrosion resistance of a corresponding nickel or nickel alloy layer.

[0016] It is comparable to a nickel alloy layer without particles. The particle-containing nickel or nickel alloy layer is therefore suitable as a protective layer against corrosion, especially in alkaline conditions.

[0017] The dispersion electrolyte according to the invention thus enables the formation of layers that offer good protection against corrosion and reduce overvoltage for electrochemical reactions in aqueous media, so that these advantageous properties can be realized simultaneously in a single layer. The particle-containing nickel or nickel alloy layer can therefore advantageously be used as a protective layer, in particular as the outermost layer on a component, especially an electronic component, for example, a contact or an electrode.

[0018] The dispersion electrolyte according to the invention comprises at least one type of particles selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof. The particles can therefore consist of one or more types of inorganic piezoelectric particles and / or one or more types of electrically conductive ceramic particles.

[0019] The particles can be made of an inorganic piezoelectric material, which can be monocrystalline or polycrystalline. A piezoelectric effect can occur with non-centrosymmetric point groups (crystal groups). The unit cell of the material therefore has no inversion center. Consequently, for example, cubic point groups with an inversion center do not exhibit piezoelectricity. If piezoelectric and non-piezoelectric modifications exist in inorganic materials, only the piezoelectric modifications are counted as particles. For example, barium titanate (BaTiO3) can exist in a perovskite structure and in a cubic modification thereof. Since the cubic modification is not piezoelectric, it is not counted as a particle. Another example is boron nitride (BN). Since hexagonal BN is piezoelectric, it can be used as a particle according to the invention.Cubic boron nitride is not piezoelectric and is therefore not considered a particle.

[0020] The particles can also be made of an electrically conductive ceramic material. Non-ceramic electrically conductive particles, such as metal particles, are not considered particles.

[0021] According to the invention, the inorganic piezoelectric particles and the electrically conductive ceramic particles are not limited. Materials doped with foreign atoms can also be used as inorganic piezoelectric particles. The particles can, for example, be made of BN (hexagonal), AlN, ZnO, GaPO 4 , M1 2y MA 1-y [MB x Ti 1-x ]O 3 , M1 2y MA 1-y [MC x Zr 1-x ]O 3 , M1 2y MA 1-y [MD x Mn 1-x] O 3 , M1 2y MA 1-y [ME x Hf 1-x ]O 3 , M1[MF x Nb 1-x ]O 3 , M1[MG x V 1-x ]O 3 , M1[MH x Ta 1-x ]O 3 , TiN, TiC, TiB 2 , Ti 2 CN, B 4 C, WC and combinations thereof can be selected.The following applies to the general formulas: M1 is in each case independently at least one element selected from Li, Na and K, preferably Li; MA is in each case independently at least one element selected from Ca, Sr, Ba, Pb and La; MB is selected from Zr, Hf, Mn, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; MC is selected from Hf, Mn, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; MD is selected from Hf, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; ME is selected from Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; MF is selected from V, Ta and Mn; MG is selected from Ta and Mn; MH is Mn; x each independently satisfies 0 ≤ x ≤ 1; and y each independently satisfies 0 ≤ y ≤ 1.

[0022] The particles are selected in particular from BN (hexagonal), AlN, ZnO, GaPO 4 , Li 2y MA 1-y [MB x Ti 1-x ]O 3 , Li 2y MA 1-y [MC x Zr 1-x ]O 3 , Li 2y MA 1-y [MD x Mn 1-x ]O 3 , LiNbO 3 , LiVO 3 , LiMnO 3 , LiTaO 3 , TiN, TiC, TiB 2 , Ti 2 CN, B 4 C, WC and combinations thereof. The following applies to the general formulas: MA is in each case independently at least one element selected from Ca, Sr, Ba, Pb and La; MB is selected from Zr, Mn and Mg 1 / 3 Nb 2 / 3 ; MC is selected from Mn and Mg 1 / 3 Nb 2 / 3 ; MD is Mg 1 / 3 Nb 2 / 3 ; x satisfies 0 ≤ x ≤ 1; and y satisfies 0 ≤ y ≤ 1.

[0023] Of the above-mentioned materials, TiN, TiC, TiB2, Ti2CN, B4C, and WC are electrically conductive ceramic materials, and the remaining materials are inorganic piezoelectric materials. According to a preferred embodiment, the particles are selected from inorganic piezoelectric particles.

[0024] According to a further preferred embodiment, the inorganic piezoelectric particles are selected from BN (hexagonal), AlN, ZnO, GaPO 4 , Li 2 [Z rx Ti 1-x ]O 3 , Li 2y MA 1-y [Zr x Ti 1-x ]O 3 , MA[Zr x Ti 1-x ]O 3 , Pb[Zr x Ti 1-x ]O 3 , LaMnO 3 and LiNbO 3 and combinations thereof. In the general formulas, the following applies: MA is in each case independently at least one element selected from Ca, Sr and Ba; x in each case independently satisfies 0 ≤ x ≤ 1; and y in each case independently satisfies 0 < y < 1.

[0025] The particles are further preferably selected from BN (hexagonal), AlN, BaTiO 3 , Li 2 ZrO 3 , Li 2 TiO 3 , CaTiO 3 , ZnO, LaMnO 3 , Pb[Zr x Ti 1-x ]O 3 (with x in the range of 0 ≤ x ≤ 1), LiNbO 3 , GaPO 4 and combinations thereof and particularly preferably from BN (hexagonal), BaTiO 3 , CaTiO 3 , Li 2 ZrO 3 and combinations thereof.

[0026] The dispersion electrolyte contains the particles, selected from inorganic piezoelectric particles and / or electrically conductive ceramic particles, in a total concentration of 1 to 200 g / L. The dispersion electrolyte contains the particles in particular in a total concentration of 3 to 150 g / L, preferably 5 to 100 g / L, more preferably 8 to 80 g / L, and even more preferably 15 to 60 g / L. At these concentrations, the dispersion electrolyte can be thoroughly mixed, and a suitable amount of particles can be deposited with the nickel or nickel alloy layer to effectively reduce the overvoltage for electrochemical reactions in aqueous media.

[0027] As a rule, the particles should be smaller than the desired layer thickness of the particle-containing nickel or nickel alloy layer. The particle size can be adjusted, for example, using common grinding and / or sieving processes, which can separate out excessively coarse or fine particles. Suitable particles are often also commercially available.

[0028] For particles with an aspect ratio of less than 3.0, the average particle diameter is typically in the range of 20 nm to 20 µm, preferably 0.1 to 10 pm, more preferably 0.5 to 8 µm. The aspect ratio indicates the ratio of the largest diameter to the smallest diameter of a particle. For spherical particles, the aspect ratio is therefore 1. The aspect ratio of the particles can be determined microscopically by measuring 20 randomly selected particles. Depending on the size of the particles, a light microscope or an electron microscope with a reference can be used.

[0029] If the particles have an aspect ratio of 3.0 or more, the average particle length is typically 0.1 to 90 µm, preferably 0.5 to 50 µm, more preferably 0.8 to 20 µm. Particles with such an aspect ratio are generally flat or elongated, for example, needle-shaped or flake-shaped. The length refers to the largest diameter of a particle.

[0030] Particle size can be determined using laser diffraction according to ISO 13320:2020, e.g., with a HELOS (Helium-Neon Laser Optical System) spectrometer. The mean particle size is expressed as a D50 value. In a deposited layer, the average particle size can be determined from a top view or cross-section using a microscope or electron microscope. At least 100 randomly selected particles are considered to determine the average particle size.

[0031] In principle, all common water-soluble nickel salts can be used for the dispersion electrolyte. The electrolyte also contains the corresponding anions of the nickel salts. Suitable examples include nickel sulfamate, nickel sulfate, nickel chloride, nickel bromide, nickel acetate, and combinations thereof. Nickel sulfamate, nickel sulfate, nickel chloride, and combinations thereof are preferred. All modifications of the nickel salts, for example, hydrates, can be used in the electrolyte. According to a preferred embodiment, the dispersion electrolyte contains sulfamate, sulfate, chloride, bromide, acetate, and combinations thereof as counteranions to the nickel ions, preferably sulfamate, sulfate, chloride, and combinations thereof.

[0032] The concentration of nickel ions in the dispersion electrolyte is 2 to 200 g / L. The nickel ions are present in the electrolyte in a concentration of 5 to 180 g / L, preferably 10 to 160 g / L, more preferably 20 to 150 g / L, and even more preferably 40 to 140 g / L. The concentration refers to the nickel ions in the form of Ni 2+< . At these concentrations, the electrolyte is stable during storage and can be operated economically with reasonable deposition rates.

[0033] Typically, high particle concentrations with high nickel ion concentrations are used in the electrolyte. Typically, the weight ratio of nickel ions to particles is in the range of 20:1 to 1:3, preferably 10:1 to 1:2, more preferably 5:1 to 1:2.

[0034] The layer deposited from the dispersion electrolyte is a particle-containing nickel layer or a particle-containing nickel alloy layer. It is preferably a particle-containing nickel layer. A dispersion electrolyte for a particle-containing nickel layer generally contains no ions of other metals—apart from any unavoidable impurities—selected from transition and / or noble metals that are electrodeposited together with nickel, or non-metal compounds that decompose during electrodeposition to form a nickel alloy and serve as precursor compounds for the incorporation of the corresponding non-metal atoms (P, S, Se, Te, and / or C) into the alloy. Such ions and / or non-metal compounds are present in the dispersion electrolyte if a particle-containing nickel alloy layer is to be deposited.

[0035] If the dispersion electrolyte contains ions of at least one further metal selected from transition metals, noble metals, and combinations thereof, these are present in a total concentration of up to 40 g / L, preferably up to 30 g / L, more preferably up to 20 g / L, and even more preferably up to 10 g / L. In this embodiment, the weight ratio of nickel ions to the ions of the further metal in the electrolyte is typically 80:20 or more, preferably 85:15 or more, more preferably 90:10 or more, even more preferably 95:5 or more.

[0036] If the dispersion electrolyte contains at least one non-metal compound selected from phosphorus compounds, sulfur compounds, selenium compounds, tellurium compounds, and combinations thereof, these are present in a total concentration of up to 50 g / L, preferably up to 30 g / L, more preferably up to 15 g / L, and even more preferably up to 5 g / L. The weight ratio of nickel ions to the total of the phosphorus atoms, sulfur atoms, selenium atoms, and tellurium atoms in the at least one non-metal compound is typically 85:15 or more, preferably 90:10 or more, more preferably 95:5 or more. The non-metal compounds thus serve as precursor compounds for P, S, Se, Te, or C atoms in a nickel alloy.

[0037] The additional metal comprises, in particular, at least one element selected from Fe, Co, Mo, Cr, Cu, Zn, Sn, Bi, Sb, and combinations thereof, and preferably consists thereof. According to a preferred embodiment, the additional metal comprises or consists of Fe, Co, Mo, or Cu. This means that, according to this embodiment, the electrolyte contains ions of one or more of these additional metals, which can be electrodeposited together with nickel. The additional metals can be added in the form of soluble salts.

[0038] The non-metal compound can in particular comprise, and preferably be selected from, at least one compound selected from hypophosphites, a urea, a thiourea, a thiocyanate, selenourea, lithium bis(trifluoromethanesulfonyl)imide, dimethyl telluride, a xanthate, a carbamate, a ketone (for example, benzalacetone), an aromatic aldehyde (for example, naphthaldehyde), Turkey red oil, and combinations thereof. During electrodeposition, the non-metal compounds can be decomposed, and P, S, Se, Te, or C atoms can be incorporated into the nickel alloy, respectively. The non-metal compound preferably comprises, or consists of, one or more compounds selected from thiourea, a thiocyanate, selenourea, lithium bis(trifluoromethanesulfonyl)imide, a xanthate, a carbamate, naphthaldehyde, benzalacetone (4-phenylbutenone), and Turkey red oil.According to this embodiment, S, Se, and / or C atoms are incorporated into the nickel alloy. S and / or Se atoms are particularly preferred. The non-metal compound then comprises or consists of at least one non-metal compound selected from thiourea, a thiocyanate, selenourea, lithium bis(trifluoromethanesulfonyl)imide, and combinations thereof.

[0039] In principle, in addition to the particles selected from inorganic piezoelectric particles, electrically conductive ceramic particles and combinations thereof, the dispersion electrolyte can also contain further particles in order to modify the properties of the particle-containing nickel or nickel alloy layer.

[0040] According to a further embodiment, the dispersion electrolyte comprises, as additional particles, electrically conductive particles made of a carbon material, preferably graphite particles, in a total concentration of 1 to 100 g / L, preferably 2 to 50 g / L, more preferably 5 to 40 g / L. These particles can be used, for example, to improve the tribological properties of the particle-containing nickel or nickel alloy layer or to reduce the contact resistance to metals. According to a further embodiment, the dispersion electrolyte contains no electrically conductive particles made of a carbon material and preferably no particles other than the particles selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof.

[0041] The further particles preferably have a particle size according to the embodiments described above for the particles.

[0042] If the dispersion electrolyte contains further particles in addition to the particles selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof, the total amount of particles, i.e., the total solids content, in the dispersion electrolyte typically does not exceed 200 g / L, preferably not 150 g / L, and more preferably not 120 g / L. Thus, good miscibility of the dispersion electrolyte and excessive agglomeration of particles in the deposited layer can be avoided.

[0043] In order to achieve efficient dispersion of the particles and, if present, of the other particles in the electrolyte and to avoid major clumping of the particles in the nickel or nickel alloy layer, the dispersion electrolyte according to the invention contains at least one anionic and / or at least one non-ionic dispersant. Typically, an anionic dispersant has sulfate groups (OSO 3 -< ), sulfonate groups (SO 3 -< ), carboxylate groups (CO 2 -< ) or carboxy groups (CO 2 H), which can then be present as anions in aqueous solution. Counterions are generally H +< , alkali metal ions, preferably K +< and / or Na +< , and / or ammonium ions (NH 4 +< ) because these result in good water solubility, can increase conductivity and do not negatively influence the electrodeposition. The electrolyte therefore also contains counterions of the anionic dispersant, preferably Na +< and / or K +< .Sulfate and sulfonate groups are dissociated, i.e., non-protonated, at the pH of the dispersion electrolyte. Carboxy groups and carboxylate groups, on the other hand, can be in equilibrium with each other.

[0044] The anionic and / or nonionic dispersant is typically used in the dispersion electrolyte at a total concentration of 0.1 to 100 g / L. It is particularly used in the electrolyte at a total concentration of 0.5 to 50 g / L, preferably 0.6 to 20 g / L. The appropriate amount of dispersant may vary depending on the type of dispersant. Generally, the more dispersant is used, the better the particle dispersion.

[0045] In the dispersion electrolyte, the weight ratio of the dispersant, selected from anionic dispersants, non-ionic dispersants and combinations thereof, to the total amount of particles (i.e. the solids content), i.e. the particles and, if present, the optional further particles, is in particular in the range of 25:1 to 1:80, preferably 5:1 to 1:60, more preferably 1:5 to 1:50.

[0046] Examples of non-ionic dispersants are polyalkylene glycol ethers, in particular polyethylene glycol ethers, alkyl polyglucosides or alkyl polyalkylene glycol ethers and combinations thereof.

[0047] According to a preferred embodiment, the dispersant comprises or consists of at least one anionic dispersant. Preferably, at least 60% by weight or more, more preferably at least 80% by weight or more, of the dispersant is one or more anionic dispersants.

[0048] According to a further preferred embodiment, the dispersant comprises or consists of at least one anionic dispersant selected from sulfate compounds having an alkyl group, an aralkyl group or an aromatic group each having up to 30 carbon atoms, sulfonate compounds having an alkyl group, an aralkyl group or an aromatic group each having up to 30 carbon atoms, and carboxy- or carboxylate-group-containing polymers.

[0049] More preferably, the anionic dispersant comprises at least one dispersant selected from sulfate compounds having an alkyl group with 6 to 24 carbon atoms, preferably with 10 to 20 carbon atoms, sulfate compounds having an aralkyl group with 6 to 24 carbon atoms, preferably with 10 to 20 carbon atoms, sulfonate compounds having an aromatic group each with 6 to 24 carbon atoms, preferably 6 to 14 carbon atoms, and combinations thereof. It may also consist of these.

[0050] According to a particularly preferred embodiment, the anionic dispersant comprises at least one first anionic dispersant selected from sulfate compounds having an alkyl group with 6 to 24 carbon atoms, preferably with 10 to 20 carbon atoms, sulfate compounds having an aralkyl group with 6 to 24 carbon atoms, preferably with 10 to 20 carbon atoms, and combinations thereof, and at least one second anionic dispersant selected from sulfonate compounds having an aromatic group with 6 to 24 carbon atoms, preferably with 6 to 14 carbon atoms. Preferably, the anionic dispersant consists of at least one first and at least one second anionic dispersant. These are used in particular in a weight ratio of first anionic dispersant to second anionic dispersant of 1:10 to 10:1, preferably 1:8 to 3:1, more preferably 1:3 to 2:1.The combination of the first and second dispersant is beneficial for effective dispersion of the particles and wetting of the surface of the substrate to be coated, which can improve deposition.

[0051] The sulfate compounds containing an alkyl group are preferably selected from alkyl sulfates, alkyl polyether sulfates, alkyl aryl polyether sulfates, and combinations thereof. The alkyl group with 6 to 24 carbon atoms, preferably 10 to 20 carbon atoms, is derived in particular from a fatty alcohol. Polyether groups are preferably polyethylene glycol groups.

[0052] The sulfonate compounds having an aromatic group with 6 to 24 carbon atoms, preferably 6 to 14 carbon atoms, are preferably selected from arylsulfonates and polymers having aromatic sulfonate groups. Particularly preferred arylsulfonates are benzenesulfonic acid, phenolsulfonic acid, and naphthalenesulfonic acid, in particular naphthalenesulfonic acid, and salts thereof. In polymers having aromatic sulfonate groups, the underlying aromatic groups preferably each have 6 to 14 carbon atoms and are derived in particular from benzenesulfonic acid, phenolsulfonic acid, and naphthalenesulfonic acid, and salts thereof. Such polymers are, for example, polycondensates of aromatic sulfonate compounds, such as benzenesulfonic acid, phenolsulfonic acid, and naphthalenesulfonic acid, or salts thereof, with formaldehyde, in particular naphthalenesulfonic acid-formaldehyde polycondensates and salts thereof, for example Tamol® from BASF SE.

[0053] According to a further preferred embodiment, the dispersion electrolyte further comprises a buffer compound having a pKa value between 2.5 and 10, and preferably selected from boric acid, acetic acid, and combinations thereof, particularly preferably boric acid. The buffer compound is used in particular at a concentration of 1 to 80 g / L, preferably 10 to 70 g / L, more preferably 20 to 60 g / L.

[0054] The pH of the dispersion electrolyte is in the range from 2.0 to 7.0, preferably 2.5 to 6.0, more preferably 3.0 to 5.0, for example 4. The pH can result directly from the constituents of the dispersion electrolyte or can be adjusted by adding acids or bases, in particular hydrochloric acid, sulfuric acid, sulfamic acid, sodium hydroxide, ammonia, potassium hydroxide or an aqueous solution thereof.

[0055] Furthermore, the dispersion electrolyte may contain conventional additives, such as those known from conventional electrolytes for the galvanic deposition of nickel layers or nickel alloy layers.

[0056] For example, conventional conducting salts can be added to increase the conductivity of the electrolyte. The conducting salt is selected, for example, from sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, ammonium chloride, sodium acetate, potassium acetate, ammonium acetate, ammonium fluoride, ammonium bifluoride, sodium fluoride, and potassium fluoride, and combinations thereof, preferably from potassium chloride, potassium sulfate, sodium chloride, and sodium sulfate, and combinations thereof.

[0057] Furthermore, complexing agents, for example, can be added to the dispersion electrolyte in order to stabilize ions of the other metal in the electrolyte and to increase the deposition rate of the other metals.

[0058] In principle, all complexing agents known to those skilled in the art and used for electrolytes can be used as complexing agents. The complexing agent is preferably a chelating, water-soluble, organic compound containing at least three functional groups selected from amino groups, carboxyl groups, and carboxylate groups. Of the functional groups, at least two are preferably amino groups. The amino groups are selected from primary, secondary, and tertiary amino groups. More preferably, the complexing agent contains one or more secondary and / or tertiary amino groups. The functional groups intended for coordination are typically spaced apart by 2 or 3 carbon atoms, allowing the formation of a stable chelate complex.

[0059] Particularly preferably, the complexing agent is at least one selected from the group consisting of EDTA, DETA, DOTA, and DOTATOC. EDTA stands for ethylenediaminetetraacetic acid. DETA denotes diethylenetriamine. DOTA stands for 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid. DOTATOC denotes a DOTA-derived complexing agent in which a DOTA molecule is linked via an amide bond to the N-terminus of an octapeptide (in particular Phe-Cys-Tyr-Lys-Thr-Cys-Thr). Other suitable complexing agents are hypophosphites, which can also lead to the incorporation of P atoms into a nickel alloy.

[0060] The dispersion electrolyte can be formed by mixing or dissolving a nickel salt, the optional salts of the other metals, the optional non-metal compounds, and the other components, i.e., dispersant, the particles, water, and optionally a buffer compound, a conductive salt, and / or a complexing agent. The particles and, if present, the other particles can advantageously be added as a powdered solid, without the need for separate dispersion or ultrasonic treatment of the mixture for dispersion. During formation of the electrolyte, stirring is preferably carried out and, if necessary, slightly heated to accelerate the dissolution or dispersion of the components. The pH can be adjusted as required, as described above.

[0061] The dispersion electrolyte according to the invention can advantageously be produced on a large scale and is thus suitable for industrial applications. The electrolyte is storable, and any settled particles can be redispersed by stirring or similar means.

[0062] As a further aspect, the present invention relates to a method for electroplating a substrate with a particle-containing nickel or nickel alloy layer. The method comprises electroplating the particle-containing nickel layer or the particle-containing nickel alloy layer onto a metallic or metallized substrate using the dispersion electrolyte according to at least one embodiment described herein. The method is carried out at temperatures in the range of 20 to 85°C, preferably 40 to 75°C, more preferably 50 to 70°C.

[0063] The process provides a coated substrate with a particle-containing nickel layer or a particle-containing nickel alloy layer, for which the advantages described above are obtained. In particular, it can be a coated substrate as described in more detail below. The process arranges the particles at least partially on the surface of the particle-containing nickel or nickel alloy layer, so that they form part of the surface. The particle-containing nickel or nickel alloy layer is typically produced as a final layer, i.e., as the outermost layer, on the substrate.

[0064] The process can be used with all common devices for the electroplating of nickel or nickel.

[0065] Nickel alloy coatings can be deposited, for example, by rack or barrel plating. Typically, the electrolyte is mixed during deposition, for example, by stirring or circulating it using a device. Stirring is preferred, for example, at 100 to 700 revolutions per minute (rpm).

[0066] The metallic or metallized substrate is connected as the cathode in the process. It can be, for example, a metallic component, for example an electronic component, for example a contact, a switch part or an electrode. The metallic or metallized substrate can consist entirely or partially of one or more metals. Example metals are aluminum, silver, copper, nickel, precious metals such as palladium or platinum, steel, stainless steel, brass and / or bronze. A metal layer that can be electroplated can also be used as the substrate, for example a metallized plastic, in particular with a metal layer made of copper, nickel, silver and / or precious metals such as palladium or platinum. The production of metallized plastics is described, for example, in DE 21 26 781 C1 or WO 2020 / 225052 A1. It can be analogous to the process described below for the electroless deposition of the particle-containing nickel or nickel.The procedure described for the nickel alloy layer should be followed.

[0067] The surface to be coated can be cleaned beforehand using conventional methods, for example, degreasing. The substrate can also be coated with one or more layers, for example, of copper, nickel, and / or silver, prior to deposition of the particle-containing nickel or nickel alloy layer, which can improve the adhesion of the particle-containing nickel or nickel alloy layer to the substrate.

[0068] Nickel anodes, for example, can be used as anodes. This makes it easy to control the nickel ion content in the electrolyte. Multiple anodes can also be used.

[0069] Furthermore, the process allows for great flexibility in process control. It can be deposited over a wide current density range, for example, with a current density of 0.1 to 10 A / dm 2 , preferably 0.5 to 5 A / dm 2 , and even more preferably 1 to 4 A / dm 2 .

[0070] In this process, the particle-containing nickel or nickel alloy layer can be deposited largely homogeneously, i.e., with a fairly uniform distribution of the particles. According to a further embodiment, the electroplating deposition can be carried out such that the particles (and / or, if present, the other particles) exhibit a gradient. For example, the particle concentration inside the nickel or nickel alloy layer can be higher than on the outside. Preferably, the particle concentration is higher outside than inside the nickel or nickel alloy layer.

[0071] A gradient can be achieved, for example, by modifying the mixing ratio, modifying the current density, or changing the particle concentration during deposition. Higher mixing generally leads to increased particle deposition. Higher current density generally leads to increased deposition of nickel or nickel alloy. Furthermore, multiple electrolytes, differing, for example, in particle concentration, nickel ion concentration, and / or the concentration of other metals or non-metallic compounds, can be used to electroplate the substrate in multiple stages.

[0072] In principle, the process can be used to produce a particle-containing nickel or nickel alloy layer of any desired thickness. For example, the particle-containing nickel or nickel alloy layer can be formed with a layer thickness of up to 200 µm or up to 100 µm. Typically, the particle-containing nickel or nickel alloy layer is deposited with a thickness of 4 to 50 µm, preferably 5 to 30 µm, and more preferably 5 to 20 µm. The layer thickness is measured using X-ray fluorescence measurement in accordance with DIN EN ISO 3497 (2001-12), for example, with a Fischerscope X-ray fluorescence measuring device XDAL for layer thicknesses up to 20 µm. For layer thicknesses exceeding 20 µm, the layer thickness is determined using a microscope at the cross-section of the layer. Typically, the deposit is carried out in such a way that the thickness of the nickel or nickel alloy is greater than the particles.

[0073] As a further aspect, the present invention provides a bath for the electroless deposition of particle-containing nickel or nickel alloy layers. The bath comprises: Nickel ions in a concentration of 2 to 200 g / L; at least one type of particle selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof, in a total concentration of 1 to 200 g / L; at least one dispersant selected from anionic dispersants, non-ionic dispersants, and combinations thereof; optionally, ions of another metal selected from transition metals, noble metals, and combinations thereof, in a total concentration of up to 50 g / L; at least one reducing agent capable of reducing nickel ions to nickel and, if present, the ions of the other metal to the other metal; and water.

[0074] The bath has a pH value of 3.0 to 12.0. The pH value is preferably 5.0 to 9.0. The electroless plating bath is also referred to below as "bath." It refers to a composition from which the particle-containing nickel layer or the particle-containing nickel alloy layer can be deposited electrolessly through one or more chemical reactions. The other metal is different from nickel.

[0075] It has surprisingly been found that the bath according to the invention can also be used to electrolessly deposit particle-containing nickel or nickel alloy layers on a substrate. The substrate can be a metallic or metallized substrate, as described above. Furthermore, as described below, plastic substrates, which are optionally nucleated, can also be coated. Advantageously, a well-adhering, dense layer, i.e., one with hardly any or no pores, can be deposited.

[0076] For the electrolessly deposited nickel or nickel alloy layer, the properties associated with the dispersion electrolyte or the galvanically deposited nickel or nickel alloy layer can be used in an analogous manner.

[0077] The advantages described above can be achieved with a nickel alloy layer. The electrolessly deposited particle-containing nickel or nickel alloy layer contains the particles, which are at least partially arranged on the surface, and nickel or a nickel alloy. Nickel and nickel alloys may contain unavoidable impurities.

[0078] The nickel alloys typically have a nickel content of 70 wt.% or more, preferably 85 wt.% or more, and more preferably 90 wt.% or more. The electrolessly deposited nickel alloys may contain the additional metal, sulfur, and / or phosphorus, as additional components.

[0079] The concentration of nickel ions in the bath is 2 to 200 g / L. The nickel ions are present in the bath in a concentration of 5 to 180 g / L, preferably 10 to 160 g / L, more preferably 20 to 150 g / L, and even more preferably 40 to 140 g / L.

[0080] The ions of the optional additional metal, selected from transition metals, noble metals, and combinations thereof, can be present in the bath at a concentration of up to 50 g / L, preferably up to 30 g / L, more preferably up to 10 g / L. The additional metal is preferably selected from Fe, Pd, Re, Ru, Sn, Cu, Co, Bi, Au, and combinations thereof. Particularly preferably, it is one or more metals selected from Fe, Co, Sn, and Bi. The additional metals can be electrolessly deposited together with nickel.

[0081] The bath is preferably used for the electroless deposition of nickel layers and nickel alloys with P and / or S and contains - apart from any unavoidable impurities - no ions of the other metals.

[0082] The bath further contains at least one reducing agent capable of reducing nickel ions to nickel and, if present, the ions of the other metal to the other metal. The reducing agent is used in a sufficient amount to reduce nickel and the optional other metals. It is used in particular at a concentration of 1 to 100 g / L, preferably 5 to 50 g / L.

[0083] The reducing agent is not particularly limited, and all reducing agents known to those skilled in the art that are suitable for the chemical deposition of nickel can be used. The reducing agent preferably comprises at least one reducing agent selected from a hypophosphite, dimethylaminoborane, NaBH4, a thiourea, a thiocyanate, and combinations thereof. It preferably consists of one or more of these reducing agents. The reducing agents can lead to the incorporation of non-metal atoms during electroless deposition. For example, the exemplary reducing agents mentioned above can result in the incorporation of P atoms, S atoms, or B atoms, respectively, so that a nickel alloy is obtained. A nickel alloy can therefore also be electrolessly deposited without ions of another metal.

[0084] With regard to the preferred and optional embodiments of the bath, reference is made to the above statements regarding the particles, their concentrations, the optional additional particles, the dispersants and the formation of the dispersion electrolyte.

[0085] The bath can be prepared in a manner analogous to the dispersion electrolyte, in particular by mixing the components and, if necessary, heating them to improve solubility. The pH can be adjusted as described above. Optionally, a complexing agent can be used, as described above.

[0086] As a further aspect, the present invention provides a method for electroless plating a substrate with a particle-containing nickel or nickel alloy layer. The method comprises electroless deposition of the particle-containing nickel layer or the particle-containing nickel alloy layer on a substrate using the bath for electroless plating of particle-containing nickel layers according to at least one embodiment described herein. The electroless deposition takes place at a temperature of 15 to 95°C, preferably 50 to 95°C, more preferably 70 to 90°C.

[0087] The process for electroless deposition of the particle-containing nickel or nickel alloy layer makes it possible to obtain a coated substrate with a particle-containing nickel layer or a particle-containing nickel alloy layer, for which the advantages described above are obtained. It can be a coated substrate as described in more detail below. The particle-containing nickel or nickel alloy layer is formed, in particular, as the outermost layer. The particles are at least partially located on the surface of the particle-containing layer, thus forming part of the surface.

[0088] The process can be used with all common devices for the electroless deposition of nickel or nickel.

[0089] Nickel alloy coatings can be applied. Typically, the bath is mixed during deposition, for example, by stirring or circulating it using a device. Stirring is preferred, for example, at 100 to 700 revolutions per minute.

[0090] According to a preferred embodiment, the substrate is arranged with the surface to be coated facing upwards, which can facilitate the incorporation of the particles into the nickel or nickel alloy layer. The deposition rate of the particles can be controlled by mixing.

[0091] In electroless deposition, no voltage is applied; instead, the nickel or nickel alloy layer is deposited by a chemical reaction. The metallic or metallized substrates described above can be used. Furthermore, plastic substrates with polar surfaces can be used directly, for example ABS or plastics functionalized by sulfonation or oxidation, in particular plastics functionalized by sulfonation. Plastics can be functionalized, for example, as described in DE 21 26 781 C1 or WO 2020 / 225052 A1, in particular the examples of these publications. The polar or functionalized plastics are preferably nucleated before the electroless deposition of the nickel or nickel alloy layer, as described, for example, in DE 21 26 781 C1 or WO 2020 / 225052 A1.During nucleation, metal nuclei, i.e., metal nuclei, are formed on the plastic surface, especially on a sulfonated plastic surface. The metal is preferably selected from the group consisting of Pd, Ag, Au, Pt, Cu, Co, Ni, and Pd / Sn.

[0092] Typically, either a solution of a metal colloid is used for nucleation, or the plastic surface, especially a sulfonated one, is first treated with a noble metal ion solution, and then the adsorbed noble metal ions are reduced to metal nuclei using a reducing agent. The use of such metal colloids is described, for example, in DE 196 11 137 and US Pat. No. 4,520,046.

[0093] The plastics are preferably selected from the group consisting of polyacrylester-styrene-acrylonitrile, polyacrylonitrile-butadiene-styrene, polyamide, polyarylamide, polyphthalamide, polyimide, polyetherimide, polyetheretherketone, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyvinyl chloride, polyethylene, polypropylene, polystyrene, syndiotactic polystyrene, polyester, polyurethane, epoxy resins and epoxy varnishes.

[0094] If necessary, the surface to be coated can be cleaned beforehand using standard methods, such as degreasing. The substrate can be coated with one or more layers of copper, nickel, and / or silver before deposition of the particle-containing nickel or nickel alloy layer.

[0095] In the method for electroless deposition of the particle-containing nickel or nickel alloy layer, a gradient can be formed. A gradient can be adjusted, for example, by varying the particle concentration during deposition. Preferably, a gradient is adjusted by using multiple baths with different nickel ion concentrations and / or different particle concentrations, with which the substrate is successively coated. Furthermore, particle-containing nickel or nickel alloy layers of any thickness can be formed, in particular according to the embodiments described above for electroplating. The above-described embodiments and embodiments therefore also apply to this method.

[0096] As a further aspect of the present invention, a coated substrate with a particle-containing nickel layer or a particle-containing nickel alloy layer is described. The particle-containing nickel or nickel alloy layer comprises: 100 parts by weight of nickel or a nickel alloy, and a total of 0.5 to 250 parts by weight of at least one type of particles selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof.

[0097] According to a preferred embodiment, the particle-containing nickel layer consists of nickel, the particles and any unavoidable impurities.

[0098] The nickel alloy typically consists of 65 wt%, preferably 75 wt% or more, more preferably 85 wt% or more, even more preferably 90 wt% or more, of nickel.

[0099] The nickel alloy contains in particular 0 wt% or more and 20 wt% or less of another metal selected from transition metals, noble metals and combinations thereof, and 0 wt% or more and 15 wt% or less of an element selected from B, P, S, Se, Te, C and combinations thereof, and the remainder consists of nickel and any unavoidable impurities. The nickel alloy contains a another metal and / or one of the elements. The other metal is different from nickel.

[0100] Unavoidable impurities can arise, for example, from the decomposition of electrolyte components and lead to the incorporation of carbon, oxygen, nitrogen and / or boron.

[0101] According to a preferred embodiment, the nickel alloy contains a particle-containing nickel alloy layer 0 wt% or more and 15 wt% or less, preferably 0 wt% or more and 10 wt% or less, more preferably 0 wt% or more and 5 wt% or less, of another metal selected from transition metals, noble metals and combinations thereof; and 0 wt% or more and 10 wt% or less, preferably 0 wt% or more and 5 wt% or less, of an element selected from B, P, S, Se, Te, C and combinations thereof, in particular P, Se and / or S, The remainder consists of nickel and any unavoidable impurities. The nickel alloy contains another metal and / or one of the elements.

[0102] The particle-containing nickel or nickel alloy layer typically forms an outermost layer on the coated substrate. The particles are at least partially arranged on the surface of the particle-containing nickel or nickel alloy layer, so that they form part of the surface of the particle-containing nickel or nickel alloy layer or the outermost layer of the coated substrate.

[0103] The particle-containing nickel or nickel alloy layer contains the particles in particular in an amount of 1 to 200 parts by weight, preferably 5 to 150 parts by weight, more preferably 10 to 100 parts by weight, based on 100 parts by weight of nickel in the case of a particle-containing nickel layer or nickel alloy in the case of a particle-containing nickel alloy layer.

[0104] The coated substrate with the particle-containing nickel or nickel alloy layer is obtainable by the method for electroplating a substrate with a particle-containing nickel or nickel alloy layer using the dispersion electrolyte according to at least one embodiment described herein, or the method for electroless plating a substrate with a particle-containing nickel or nickel alloy layer using the bath according to at least one embodiment described herein. Therefore, the advantages described above are obtained.

[0105] According to one embodiment, the coated substrate is obtained by the process for the electroplating of a particle-containing nickel or nickel alloy layer. The particle-containing nickel alloy then contains in particular 0 wt% or more 20 wt% or less, preferably 0 wt% or more and 15 wt% or less, more preferably 0 wt% or more and 10 wt% or less, even more preferably 0 wt% or more and 5 wt% or less, of a further metal selected from transition metals, noble metals and combinations thereof, and 0 wt% or more and 15 wt% or less, preferably 0 wt% or more and 10 wt% or less, more preferably 0 wt% or more and 5 wt% or less of an element selected from P, S, Se, Te, C and combinations thereof, in particular P, Se and / or S, and the remainder consists of nickel and any unavoidable impurities. The nickel alloy contains another metal and / or one of the elements. Metal preferably comprises or consists of Fe, Co, Mo, Cr, Cu, Zn, Sn, Bi, Sb, and combinations thereof. More preferably, the additional metal comprises or consists of one or more metals selected from Fe, Co, Mo, and Cu. The substrate is a metallic or metallized substrate as described herein.

[0106] The nickel alloy obtained by electrodeposition is preferably an alloy of Ni and Fe, Ni and Co, Ni and Mo, Ni and Cr, Ni and Cu, Ni and P, Ni and S, Ni and Se, Ni and Fe and P, Se and / or S, Ni and Co and P, Se and / or S, Ni and Mo and P, Se and / or S, Ni and Cr and P, Se and / or S, or Ni and Cu and P, Se and / or S, in each case with any unavoidable impurities.

[0107] According to one embodiment, the coated substrate is obtained by the process for the electroless deposition of a particle-containing nickel or nickel alloy layer. The particle-containing nickel alloy then contains in particular 0 wt% or more 20 wt% or less, preferably 0 wt% or more and 15 wt% or less, more preferably 0 wt% or more and 10 wt% or less, even more preferably 0 wt% or more and 5 wt% or less, of a further metal selected from transition metals, noble metals and combinations thereof, 0 wt% or more and 15 wt% or less, preferably 0 wt% or more and 10 wt% or less, of an element selected from B, P, S and combinations thereof, in particular P and / or S, and consists of nickel and any unavoidable impurities. The nickel alloy contains another metal and / or one of the elements. The other metal is preferably selected from Fe, Pd, Re, Ru, Sn, Cu, Co, Bi, Au, and combinations thereof. The other metal is particularly preferably selected from Fe, Co, Sn, Bi, and combinations thereof. The substrate is one of the substrates described above in connection with the methods.

[0108] Furthermore, the optional and preferred embodiments described above apply analogously to the coated substrate. This applies in particular to the substrate coated with the particle-containing nickel or nickel alloy layer, the layer thicknesses, the particle sizes, the optional additional particles, and the optional particle gradient.

[0109] If present, the additional particles of a conductive carbon material are present in the particle-containing layer in an amount of 1 to 100 parts by weight, preferably 2 to 50 parts by weight, more preferably 3 to 30 parts by weight, based on 100 parts by weight of nickel in the case of a particle-containing nickel layer or nickel alloy in the case of a particle-containing nickel alloy layer. The total amount of particles then typically does not exceed 250 parts by weight, preferably not 200 parts by weight, more preferably not 150 parts by weight, based on 100 parts by weight of nickel in the case of a particle-containing nickel layer or nickel alloy in the case of a particle-containing nickel alloy layer.

[0110] The particle-containing nickel or nickel alloy layer is particularly mechanically stable and corrosion-resistant in the weakly acidic, neutral and alkaline range, i.e. in a pH range of 4 or more, in particular 6 or more.

[0111] According to a further embodiment, the particle-containing nickel or nickel alloy layer has a hardness of at least HV 200 (Vickers hardness), preferably at least HV 300, and more preferably at least HV 400. The measurement is carried out on the surface according to DIN EN ISO 14577-1 (2015-11). The hardness can be adjusted in particular via the particle content and, if present, the content of other particles.

[0112] The coated substrate is corrosion-resistant in weakly acidic and especially alkaline media and, compared to a substrate coated with a corresponding nickel or nickel alloy layer without the particles, exhibits a reduced overvoltage in aqueous alkaline media. The coated substrate can therefore be used, for example, as an electronic component, in particular as a switch, contact, electrode, or other component of an electrochemical cell. It is preferably used as an electrode of an electrochemical cell, for example in chlor-alkali electrolysis or the electrolysis of water or aqueous alkaline media, such as for the formation of oxygen and hydrogen. It can be used independently as an anode, as a cathode, or as an anode and as a cathode.

[0113] The dispersion electrolyte according to the invention and the bath according to the invention can therefore be used for producing an electronic component, in particular for producing a switch, a contact, an electrode and a component of an electrochemical cell, preferably an electrode.

[0114] As a further aspect, the present invention provides an electrochemical cell comprising the coated substrate according to at least one embodiment. The coated substrate preferably serves as an electrode. It can be used independently as an anode, as a cathode, preferably as an anode and as a cathode. Examples of an electrochemical cell are a redox flow battery, a fuel cell, and an electrolyzer.

[0115] According to one embodiment, the coated substrate is used as the cathode of an electrolyzer. The anode can then also be a coated substrate according to the invention or another electrode, for example made of nickel or a nickel alloy, or an electrode coated with nickel or a nickel alloy. Examples

[0116] The present invention is illustrated below by examples. It is not limited to these examples. Measurement method

[0117] The following measurement methods were used. 1) Layer thickness

[0118] The coating thickness was measured using a Fischerscope X-ray fluorescence measuring device (XDAL) in accordance with DIN EN ISO 3497 (2001-12). An averaged measurement value is provided. 2) Composition

[0119] The composition of the particle-containing nickel or nickel alloy layer was also analyzed by X-ray fluorescence analysis on the coated substrate surface using the aforementioned device in accordance with DIN EN ISO 3497 (2001-12). The measured area was approximately 200 x 150 µm. The measured values ​​are obtained with an accuracy of ± 2 wt% or better. 3) Vickers hardness

[0120] The hardness test was performed according to DIN EN ISO 14577-1 (2015-11) on the surface of the deposited layer, if necessary after polishing (i.e., conditioning). The Vickers hardness is indicated by the symbol "HV." A weight of 200 g was used as the test force. The test duration was 10 s. Vickers hardness is expressed dimensionlessly. Preparation of the metallic substrates

[0121] Stainless steel sheets (1.4404) measuring 50 x 120 x 0.4 mm were used for the tests. These were pretreated as follows: 1 Degreasing Degreasing SLOTOCLEAN AK 160 65°C 5 minutes 2 Wash Water RT* 3 Pickling aqueous HCl, 18%, with SLOTOCLEAN BEF 30 RT 10 s 4 Wash Water RT 5 Cathodic degreasing Degreasing SLOTOCLEAN EL DCG, 6 A / dm 2< RT 2 minutes 6 Wash Water RT 7 Decapping aqueous HCl, 10% RT 30 s 8 Wash Water RT 9 Deposition intermediate layer Nickel Strike, 3 A / dm 2 RT 6 minutes ∗< RT = Room temperature Reagents

[0122] The following reagents were used for the experiments, among others.

[0123] Slotoclean AK 160 (contains NaOH and disodium metasilicate), SLOTOCLEAN EL DCG (contains NaOH, disodium metasilicate, and sodium carbonate), and SLOTOCLEAN BEF 30 (contains but-2-yne-1,4-diol and ethoxylated isotridecanol) are products of Dr.-Ing. Max Schlötter.

[0124] Nickel Strike: Nickel electrolyte for the electrodeposition of the intermediate layer, Dr.-Ing. Max Schlötter, containing 180 g / L NiCl 2 ·6H 2 O according to DIN 50970, 8 g / L HCl (concentrated), water

[0125] Nickel sulfamate bath MS: Nickel sulfamate solution in water from Dr.-Ing. Max Schlötter, containing 160 g / L nickel ions, pH 4.0

[0126] SLOTONIK M: Bath additive from Dr.-Ing. Max Schlötter, containing 3 to 5 wt.% alkyl ether sulfate as sodium salt, alkyl group C12-14, polyethylene glycol ether with an average of 2 ethylene oxide units. Barium titanate (BaTiO 3 , perovskite structure): particle size 0.8 µm (aspect ratio < 3.0) from Sigma-Aldrich, CAS: 12047-27-7 Boron nitride (BN, hexagonal): particle size approximately 1 pm, flake-shaped (aspect ratio > 3.0) from Sigma-Aldrich, CAS: 10043-11-5 Titanium nitride (TiN): particle size <3 µm (aspect ratio < 3.0) from Sigma-Aldrich, CAS: 25583-20-4 Tamol ®< : naphthalenesulfonic acid-formaldehyde polycondensates (sodium salts) from BASF SE Examples 1 to 9 and Comparative Example 1 Production of electrolytes

[0127] For Examples 1 to 9 and Comparative Example 1 (VB1), electrolytes with the following components were prepared in a glass beaker (2 L). 375 mL / L nickel sulfamate bath MS (equivalent to 60 g / L nickel) 34 g / L NiCl 2 6H 2 O (equivalent to 8.4 g / L nickel) 45 g / L boric acid 8 mL / L SLOTONIK M (bath additive with dispersant) 0.9 g / L Tamol ®< (dispersant) distilled water barium titanate (BaTiO 3 ), boron nitride (BN) or titanium nitride (TiN) according to Table 1

[0128] For this purpose, NiCl 2 .6H 2 O, dispersant, and boric acid were first added to a mixture of distilled water, the nickel sulfamate solution, and the bath additive, and dissolved while stirring (500 rpm) at 60°C. For dissolution, the pH was adjusted to 4.1 by adding KOH. Then, powdered barium titanate (BaTiO 3 ) in Examples 1 to 3, powdered boron nitride (BN) in Examples 4 to 6, and powdered titanium nitride (TiN) in Examples 7 to 9 were slowly added and dispersed while stirring (500 rpm). In Comparative Example 1, no particles were added. The pH was adjusted to 4.0 by adding sulfamic acid. The amount of electrolyte was 2 L in each case. Table 1 BaTiO 3 (perovskite structure) [g / L] BN (hexagonal) [g / L] TiN [g / L] Example 1 1 - - Example 2 20 - - Example 3 40 - - Example 4 - 1 - Example 5 - 10 - Example 6 - 20 - Example 7 - - 1 Example 8 - - 10 Example 9 - - 20 Comparison example 1 - - - Galvanic coating

[0129] Stainless steel sheets were pretreated as described above and precoated with a nickel layer. The resulting metallic substrates were then electroplated as follows.

[0130] The electrolyte was mixed in a 2 L glass beaker using a 40 mm stir bar (500 rpm). The stainless steel sheets served as the cathode and were immersed 10 cm deep into the electrolyte. Two Ni electrodes (25 x 120 x 5 mm) served as the anode, arranged parallel to the cathode on either side at a distance of 4 cm. The anodes were also immersed to a depth of 10 cm. The two parallel anodes were connected in series with the electrolyte, the cathode, and a direct current source. Deposition was carried out at 60°C and a current density of 2.5 A / dm² for 20 min. Assessment of the deposited layers

[0131] In Examples 1 to 9 and Comparative Example 1 (VB1), dense, pore-free, and well-adhering nickel layers were deposited. The layer thicknesses were approximately 10 µm.

[0132] The Fig. 1 to 3 show scanning electron microscope images of examples 1 to 3 at a magnification of 3000. In example 1, at a concentration of 1 g / L in the dispersion electrolyte, isolated barium titanate particles were integrated into the nickel layer. At the higher concentrations of 20 g / L and 40 g / L barium titanate in the dispersion electrolytes of examples 2 and 3, more particles were incorporated into the layer, as shown in the Fig. 2 and 3 can be seen. Particles on the surface of the nickel layer appear as brighter, sharply defined areas. Larger, round, dark areas indicate deeper, nickel-coated particles. Fig. 1 to 3demonstrate that barium titanate particles were incorporated into the respective nickel layer and are partially located on the surface of the nickel layer. In Examples 2 and 3 in particular, the incorporation occurred quite evenly across the entire surface.

[0133] Fig. 4 shows a photograph of Comparative Example 1 without particles in the nickel layer at a magnification of 500.

[0134] Cross sections of the coated substrates showed that the barium titanate particles were also deposited homogeneously inside the particle-containing nickel layer of Examples 1 to 3. In the Fig. 5A , 6A and 7 are shown light microscope images of the cross-section of the coated substrates of Examples 2 and 3 as well as Comparative Example 1. In the Fig. 5A and 6A The particles in the coating are already visible. In the Fig. 5B and 6BScanning electron microscope images of the cross sections of Example 2 and Example 3 are shown at a magnification of 1500.

[0135] The Fig. 8 to 10 show scanning electron microscope images of examples 4, 5 and 6 at a magnification of 5000 for example 4 ( Fig. 8 ) and 2000 for examples 5 and 6 ( Fig. 9 or 10). The Fig. 8 It can be seen that boron nitride was already incorporated into the nickel layer at a concentration in the dispersion electrolyte of 1 g / L. As in Fig. 9 As can be seen, at a concentration of 10 g / L, more boron nitride particles were incorporated into the nickel layer. The piezoelectric, i.e. non-electrically conductive, boron nitride particles are in Fig. 9 as bright areas. The boron nitride particles therefore form part of the surface of the particle-containing nickel layer. Agglomerates of several particles were occasionally observed. As shown in Fig. 10As can be seen, at a concentration of 20 g / L in the dispersion electrolyte, significantly more boron nitride particles were incorporated into the nickel layer. Particularly in Examples 5 and 6, the incorporation occurred quite evenly across the entire layer.

[0136] Cross sections of the coated substrates of Examples 4, 5 and 6 again showed a homogeneous incorporation of the boron nitride particles into the interior of the coating. Fig. 11A and 12A show light microscope images of cross sections of example 5 and example 6. In the Fig. 11B and 12B Scanning electron microscope images of it are shown.

[0137] The Fig. 13 to 15 show scanning electron microscope images of examples 7, 8 and 9 at a magnification of 500. Fig. 13demonstrates the isolated incorporation of titanium nitride particles into the nickel layer at a concentration in the dispersion electrolyte of 1 g / L. In Examples 8 and 9, at higher concentrations of 10 g / L and 20 g / L, respectively, more titanium nitride particles were deposited with the layer (see Fig. 14 or 15).

[0138] Cross sections of the coated substrates of Examples 7, 8 and 9 again showed a homogeneous incorporation of the titanium nitride particles into the interior of the layer. Fig. 16A and 17A show light microscope images of cross sections of example 8 and example 9. In the Fig. 16B and 17B Scanning electron microscope images of it are shown.

[0139] The composition was determined for Examples 2, 3, 6, 8, 9 and Comparative Example 1 (VB1) (see Table 2). Table 2 Example / Element 2 [wt.%] 3 [wt.%] 6 [wt.%] 8 [wt.%] 9 [wt.%] VB1 [wt.%] B - - 7,8 - - - C 8,0 7,3 9,6 7,5 5,5 6,5 N - - 3,4 4,5 10,4 - O 4,7 11,0 2,7 3,3 3,5 3,8 Ni 74,6 44,0 76,5 76,6 58,0 89,7 Ti 2,7 11,4 - 8,0 22,4 - Ba 9,9 26,4 - - - -

[0140] It is assumed that the measured C and O amounts are due to natural impurities or electrolyte components. In Examples 2 and 3, part of the O content is due to the barium titanate particles. The incorporation of barium titanate, boron nitride, and titanium nitride, respectively, was confirmed based on the measured compositions.

[0141] Furthermore, the Vickers hardness (HV) was determined. The results are summarized in Table 3. Table 3 Particles in the electrolyte AGM Comparison example 1 - 166 Example 1 1 g / L BaTiO3 412 Example 2 20 g / L BaTiO3 610 Example 3 40 g / L BaTiO3 643 Example 4 1 g / L BN 412 Example 5 10 g / L BN 432 Example 6 20 g / L BN 452 Example 7 1 g / L TiN 379 Example 8 10 g / L TiN 593 Example 9 20 g / L TiN 629

[0142] The incorporation of the particles was accompanied by an increase in the Vickers hardness of the layer. Measurement of overvoltages

[0143] The overpotential was determined in an electrochemical cell from Gaskatel (Flexcell PP) with a sample area of ​​3 cm². The overpotentials were measured for the alkaline electrolysis of water in 30% aqueous KOH. The potential at which a current flow was observed was determined for the evolution of hydrogen (HER) or oxygen (OER). The coated substrate was used as an electrode in a chamber and connected as the cathode or anode, respectively. A standard hydrogen electrode (Gaskatel Hydroflex) served as the reference electrode. The counterelectrode used consisted of wound Pt wire.

[0144] The overpotential was taken as the measured potential at 25°C for a current of -10 mA (-3.3 mA / cm 2 ) minus the theoretical potential of 0 V for hydrogen (HER) or at 25°C for a current of 10 mA (3.3 mA / cm 2 ) minus the theoretical potential of +1.23 V for oxygen (OER). The smaller the magnitude of the overpotential, i.e., the closer the measured value is to 0, the lower the overpotential.

[0145] The results are summarized in Table 4. Table 4 Particles in the electrolyte HER [V] OER [V] Comparison example 1 - -1,09 +0,17 Example 1 1 g / L BaTiO3 -0,78 +0,26 Example 2 20 g / L BaTiO3 -0,54 +0,29 Example 3 40 g / L BaTiO3 -0,38 +0,29 Example 4 1 g / L BN -0,81 +0,24 Example 5 10 g / L BN -0,78 +0,21 Example 6 20 g / L BN -0,33 +0,31 Example 7 1 g / L TiN -0,55 +0,27 Example 8 10 g / L TiN -0,53 +0,30 Example 9 20 g / L TiN -0,58 +0,29

[0146] Compared to Comparative Example 1, the incorporation of small amounts of piezoelectric barium titanate in Example 1 and of piezoelectric boron nitride in Example 4 resulted in a total reduction of the overpotentials, namely by approximately 0.2 V. The overpotential for hydrogen formation was significantly reduced; a slight increase occurred for oxygen formation.

[0147] The effect was significantly enhanced by the increased incorporation of barium titanate particles in Examples 2 and 3 and by the increased incorporation of boron nitride particles in Examples 5 and 6. In Examples 3 and 6, the overpotentials were reduced by a total of approximately 0.6 V. It was observed that the overpotential for hydrogen formation could be significantly reduced. A slight increase was observed for oxygen formation compared to Comparative Example 1.

[0148] Thus, it was confirmed that the incorporation of piezoelectric barium titanate particles or piezoelectric boron nitride particles can reduce overpotentials in aqueous alkaline media. A greater reduction in overpotential was observed at higher particle concentrations.

[0149] Even with titanium nitride, an electrically conductive ceramic material, a significant reduction in the overvoltage of approximately 0.4 V was observed even with a low particle content in the dispersion electrolyte of Example 7. In contrast to the piezoelectric materials barium titanate and hexagonal boron nitride, no further reduction in the overvoltage was observed by increasing the particle concentration in the nickel layer; instead, it remained approximately constant. It is possible that the electrically conductive ceramic titanium nitride reduces the overvoltage via a different mechanism than the piezoelectric particles in Examples 1 to 6.

[0150] As shown in Examples 1 to 9, the coated substrates from Examples 1 to 9 are suitable as anodes and, in particular, as cathodes for electrolysis in aqueous alkaline media. Significantly reduced overpotentials were measured, particularly for the cathode reaction, i.e., the formation of hydrogen.

Claims

1. A dispersion electrolyte for the electrodeposition of particle-containing nickel or nickel alloy layers, comprising: - nickel ions in a concentration of 2 to 200 g / L; - at least one type of particle selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof, in a total concentration of 1 to 200 g / L; - at least one dispersant selected from anionic dispersants, non-ionic dispersants, and combinations thereof; - optionally, ions of at least one further metal selected from transition metals, noble metals, and combinations thereof, in a total concentration of up to 40 g / L;- optionally at least one non-metallic compound other than the dispersant and selected from phosphorus compounds, sulfur compounds, selenium compounds, tellurium compounds, carbon compounds, and combinations thereof, in a total concentration of up to 50 g / L; and - water, wherein the dispersion electrolyte has a pH of 2.0 to 7.

0.

2. Dispersion electrolyte according to claim 1, wherein the particles are made of BN (hexagonal), AlN, ZnO, GaPO4, M1 2y MA 1-y [MB x Ti 1-x ]O3, M1 2y MA 1-y [MC x Zr 1-x ]O3, M1 2y MA 1-y [MD x Mn 1-x ]O3, M1 2y MA 1-y [ME x Hf 1-x ]O3, M1[MF x Nb 1-x ]O3, M1[MG x V 1-x ]O3, M1[MH x Ta 1-x]O3, TiN, TiC, TiB2, Ti2CN, B4C, WC and combinations thereof, and wherein in the general formulas the following applies: M1 is in each case independently at least one element selected from Li, Na and K, preferably Li; MA is in each case independently at least one element selected from Ca, Sr, Ba, Pb and La; MB is selected from Zr, Hf, Mn, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; MC is selected from Hf, Mn, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; MD is selected from Hf, Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3 ; ME is selected from Mg 1 / 3 Nb 2 / 3 , Mg 1 / 3 V 2 / 3 , Mg 1 / 3 Mn 2 / 3 and Mg 1 / 3 Ta 2 / 3; MF is selected from V, Ta, and Mn; MG is selected from Ta and Mn; MH is Mn; x each independently satisfies 0 ≤ x ≤ 1; and y each independently satisfies 0 ≤ y ≤ 1.

3. Dispersion electrolyte according to claim 2, wherein the particles are made of BN (hexagonal), AlN, ZnO, GaPO4, Li2[Zr x Ti 1-x ]O3, Li 2y MA 1-y [Zr x Ti 1-x ]O3, MA[Zr x T i-x ]O3, Pb[Zr x Ti 1-x ]O3, LaMnO3 and LiNbO3 and combinations thereof, and wherein each MA is independently at least one element selected from Ca, Sr and Ba; each x independently satisfies 0 ≤ x ≤ 1; and each y independently satisfies 0 < y < 1.

4. Dispersion electrolyte according to one of the preceding claims, wherein in the dispersion electrolyte the weight ratio of nickel ions to the ions of the further metal is 80:20 or more, preferably 85:15 or more, more preferably 90:10 or more, even more preferably 95:5 or more, and / or the weight ratio of nickel ions to the total of the phosphorus atoms, sulfur atoms, selenium atoms, tellurium atoms and carbon atoms in the at least one non-metal compound is 85:15 or more, preferably 90:10 or more, more preferably 95:5 or more.

5. Dispersion electrolyte according to one of the preceding claims, wherein the further metal comprises at least one element selected from Fe, Co, Mo, Cr, Cu, Zn, Sn, Bi, Sb and combinations thereof, and / or the non-metal compound comprises at least one compound selected from hypophosphites, a urea, a thiourea, a thiocyanate, selenourea, lithium bis(trifluoromethanesulfonyl)imide, dimethyl telluride, a xanthate, a carbamate, a ketone, an aromatic aldehyde, Turkey red oil and combinations thereof.

6. Dispersion electrolyte according to one of the preceding claims, wherein the dispersant comprises at least one anionic dispersant selected from sulfate compounds having an alkyl group, an aralkyl group or an aromatic group each having up to 30 carbon atoms, sulfonate compounds having an alkyl group, an aralkyl group or an aromatic group each having up to 30 carbon atoms, and carboxy- or carboxylate-group-containing polymers.

7. The dispersion electrolyte according to claim 6, wherein the anionic dispersant comprises at least a first anionic dispersant selected from sulfate compounds having an alkyl group having 6 to 24 carbon atoms, sulfate compounds having an aralkyl group having 6 to 24 carbon atoms, and combinations thereof, and at least a second anionic dispersant selected from sulfonate compounds having an aromatic group having 6 to 24 carbon atoms.

8. A bath for the electroless deposition of particle-containing nickel or nickel alloy layers, comprising: - nickel ions in a concentration of 2 to 200 g / L; - at least one type of particle selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof, in a total concentration of 1 to 200 g / L; - at least one dispersant selected from anionic dispersants, non-ionic dispersants, and combinations thereof; - optionally, ions of another metal selected from transition metals, noble metals, and combinations thereof, in a total concentration of up to 50 g / L; - at least one reducing agent capable of reducing nickel ions to nickel and, if present, the ions of the other metal to the other metal; and - water, wherein the bath has a pH of 3.0 to 12.

0.

9. Bath according to claim 8, wherein the reducing agent comprises at least one reducing agent selected from hypophosphites, dimethylaminoborane, NaBH4, a thiourea, a thiocyanate and combinations thereof, and / or wherein the further metal is selected from Fe, Pd, Re, Ru, Sn, Cu, Co, Bi, Au and combinations thereof.

10. A method for electroplating a substrate with a particle-containing nickel or nickel alloy layer, comprising electroplating the particle-containing nickel or nickel alloy layer on a metallic or metallized substrate using the dispersion electrolyte according to any one of claims 1 to 7 at a temperature of 20 to 85°C.

11. A method for electroless plating a substrate with a particle-containing nickel or nickel alloy layer, comprising electroless depositing the particle-containing nickel or nickel alloy layer on a substrate using the bath according to claim 8 or 9 at a temperature of 15°C to 95°C.

12. A coated substrate with a particle-containing nickel or nickel alloy layer, wherein the particle-containing nickel or nickel alloy layer comprises - 100 parts by weight of nickel or nickel alloy, and - a total of 0.5 to 250 parts by weight of at least one type of particles selected from inorganic piezoelectric particles, electrically conductive ceramic particles, and combinations thereof.

13. The coated substrate of claim 12, wherein the nickel alloy contains at least 65 wt% nickel.

14. The coated substrate according to claim 12, wherein the nickel alloy contains - 0 wt.% or more and 20 wt.% or less of another metal selected from transition metals, noble metals, and combinations thereof; and - 0 wt.% or more and 15 wt.% or less of an element selected from B, P, S, Se, Te, C, and combinations thereof, and the remainder consists of nickel and any unavoidable impurities, and wherein the nickel alloy contains another metal and / or one of the elements.

15. The coated substrate of claim 14, wherein the further metal is selected from Fe, Co, Mo, Cr, Cu, Zn, Sn, Bi, Sb and combinations thereof and the element is selected from P, S, Se, Te, C and combinations thereof, or the further metal is selected from Fe, Pd, Re, Ru, Sn, Cu, Co, Bi, Au and combinations thereof and the element is selected from B, P, S and combinations thereof.

16. An electrochemical cell comprising the coated substrate according to any one of claims 12 to 15.

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