METALLIC COATING AND A METHOD FOR PRODUCING THE SAME

Abstract

The present invention relates to metal plating solution comprising at least one source of metal ions and detonation nanodiamonds, wherein the detonation nanodiamonds are substantially free of negatively charged functionalities, and to a method for producing the solution. The present invention further relates to metal plating method and to a metallic coating comprising metal and detonation nanodiamonds substantially free of negatively charged functionalities.

Claims

1. An electroless metal plating solution comprising at least one source of metal ions, a reducing agent and detonation nanodiamonds, wherein acid value of the detonation nanodiamonds is less than 5.0.

2. The electroless metal plating solution according to claim 1, wherein the metal is selected from the group consisting of nickel, copper, gold, cobalt, palladium, iron, silver, and mixtures thereof.

3. The electroless metal plating solution according to claim 2, wherein the metal is nickel.

4. The electroless metal plating solution according to claim 1, wherein amount of the detonation nanodiamonds in the plating solution is 0.005-15 g/l.

5. The electroless metal plating solution according to claim 1, wherein particle size distribution D90 of the detonation nanodiamond dispersion added to the electrolyte is not more than 100 nm.

6. The electroless metal plating solution according to claim 1, wherein the detonation nanodiamond dispersion exhibits zeta potential at least +40 mV, measured with Laser Doppler Micro-electrophoresis

7. The electroless metal plating solution according to claim 1, wherein acid value of the detonation nanodiamonds is 0.

8. The electroless metal plating solution according to claim 1, wherein the solution further comprises additional components selected from the group consisting of graphite, graphene, carbon nanotubes, diamond particles larger than 15 nm, boron carbide, chromium carbide, calcium fluoride, tungsten carbide, titanium carbide, polytetrafluoroethylene (PTFE), boron nitride, silicon carbide, aluminium oxide, silicon dioxide, any other solid particle additives and mixtures thereof.

9. A method for producing the electroless metal plating solution according to claim 1, said method comprising the steps of adding detonation nanodiamonds having acid value less than 5.0 to a solution comprising at least one source of metal ions and a reducing agent; and mixing the solution.

10. The method according to claim 9, wherein the detonation nanodiamonds are added as aqueous dispersion.

11. The method of claim 10, wherein the aqueous dispersion is free of surfactants.

12. The method according to claim 9, wherein particle size distribution D90 of the detonation nanodiamond dispersion added to the electrolyte is not more than 100 nm.

13. The method according to claim 9, wherein the detonation nanodiamond dispersion added to the electrolyte exhibits zeta potential at least +40 mV, measured with Laser Doppler Micro-electrophoresis.

14. An electroless plating method comprising immersing a substrate into a plating bath comprising the electroless metal plating solution according to claim 1.

15. The electroless plating method according to claim 14, wherein the method further comprises step of heat treating the formed plating.

16. A metallic coating comprising metal and detonation nanodiamonds, wherein acid value of the detonation nanodiamonds is less than 5.0.

17. The metallic coating according to claim 16, wherein the acid value of the detonation nanodiamonds is 0.

18. The metallic coating according to claim 16, wherein amount of the detonation nanodiamonds is 0.01-4.0 wt. % based on the total weight of the coating.

19. The metallic coating according to claim 16, wherein reduction in Taber Wear Index (TWI) is at least 10% as compared to a metallic coating without detonation nanodiamonds.

20. The metallic coating according to claim 16, wherein coating coefficient of friction is not increased by more than 15%, as compared to coating without detonation nanodiamond additives.

21. The metallic coating according to claim 16, wherein coating corrosion resistance, as measured by neutral salt spray test, is not reduced by more than 5 R.sub.p units, as compared to coating without nanodiamond additives.

22. The metallic coating according to claim 16, wherein the coating has been subjected to heat treating.

23. The metallic coating according to claim 22, wherein reduction in TWI is more than 100%, as compared to metallic coating without detonation nanodiamonds.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0053] FIG. 1 presents friction coefficients of as-plated samples according to the present invention and reference against Al.sub.2O.sub.3.

[0054] FIG. 2 presents friction coefficients of samples according to the present invention and reference annealed in 400 C. for 1 hour against Al.sub.2O.sub.3.

[0055] FIG. 3 presents friction coefficients of samples according to the present invention and reference annealed in 400 C. for 1 hour against steel.

[0056] FIG. 4 presents friction coefficients of electrolytic nickel, NiSiC, Ni-ND 0.01 g/, Ni-ND 1 g/l and Ni-ND 7.5 g/l according to the present invention.

[0057] FIGS. 5a and 5b presents SEM images of wear tracks of electrolytic nickel and Ni-ND Hydrogen D 7.5 g/l according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0058] In a first aspect of the present invention there is provided an electroless metal plating solution. Said metal plating solution can also be an electrolytic metal plating solution.

[0059] More particularly there is provided an electroless metal plating solution, also referred as to an electrolyte, comprising at least one source of metal ions and detonation nanodiamonds, wherein the detonation nanodiamonds are substantially free of negatively charged functionalities.

[0060] The metal is selected from a group consisting nickel, copper, gold, cobalt, palladium, iron and silver, or mixtures thereof, preferably the metal is nickel.

[0061] In one embodiment of the source of nickel ions is selected from a group consisting of nickel sulphate, nickel chloride, nickel acetate, nickel methyl sulfonate, or mixtures thereof.

[0062] Amount of the metal in the plating solution can be adjusted depending on the wanted properties of coating forming in the electroless metal plating process. In one embodiment amount of the metal in the plating solution is 0.1-10 g/l, preferably 3-6.5 g/l.

[0063] Precursor nanodiamond material may be substantially pure detonation nanodiamond material, preferably having a nanodiamond content of at least 87% by weight, more preferably at least 97% by weight. The detonation nanodiamond may contain graphite and amorphous carbon originating from the production of the detonation nanodiamonds. They may also contain some residual metal impurities, either as metals, metal salts or in metal oxide, nitride or halogenate form.

[0064] The detonation nanodiamonds according to this invention are substantially free of negatively charged functionalities. By term substantially free of negatively charged functionalities is meant that the applied detonation nanodiamond material acid value is less than 5.0. A comprehensive description on determining the acid value can be found in example section.

[0065] The detonation nanodiamond surface contained acidic terminal group can be determined by Boehm titration method. Boehm titration is a widely used method to determine acidic terminal groups on carbon materials. The basic principle of the method is that the surface oxygen groups of carbon material with acidic properties (carboxyl, lactone and phenol) can be identified by neutralizing them with bases of different strengths. The method is most often used to determine the amount of surface carboxyl groups, which can be neutralized with a weak base, sodium bicarbonate (NaHCO.sub.3).

[0066] In one embodiment the detonation nanodiamond acid value is less than 4.0, preferably less than 3.5, such as 0-3.5.

[0067] Examples of negatively charged functionalities include but are not limited to carboxylic acid, sulfonic and nitric acid functionalities and their various salts.

[0068] In a preferred embodiment the detonation nanodiamonds are free of negatively charged functionalities, that is, the acid value is 0.

[0069] The absence of the nanodiamond surface contained acidic, negatively charged functionalities can be measured and secured by Boehm titration, which method is more comprehensively described in Rivka Fidel, Evaluation and implementation of methods for quantifying organic and inorganic components of biochar alkalinity, Iowa State University, Digital Repository at Iowa State University, 2012. The method is based on the principle that strong acids and bases will react with all bases and acids, respectively, whereas the conjugate bases of weak acids will accept protons only from stronger acids (i.e. acids with lower pKa values).

[0070] Examples of functionalities on detonation nanodiamond that are not negatively charged are hydrogen, amine and hydroxyl termination. Such detonation nanodiamonds are commercially available. In one preferred embodiment the detonation nanodiamond is functionalized with hydrogen and/or amine functionalities.

[0071] In one embodiment of the present invention the detonation nanodiamond may include detonation soot such as graphitic and amorphous carbon, the content of oxidisable carbon preferably being at least 5 wt.-%, more preferably at least 10 wt.-%.

[0072] Preferably the detonation nanodiamonds are in single digit form. In one embodiment the detonation nanodiamond particles in single digit form have an average primary particle size of from 1 nm to 10 nm, preferably from 2 nm to 8 nm, more preferably from 3 nm to 7 nm, and most preferably from 4 nm to 6 nm. Such particle size can be determined for example by TEM (Tunneling Electron Microscope).

[0073] In one embodiment particle size distribution D90 of the detonation nanodiamond dispersion is not more than 100 nm, such as 1-100 nm, preferably not more than 20 nm, such as 1-20 nm, most preferably not more than 12 nm, such as 1-12 nm. Such particle size distribution can be measured for example by dynamic light scattering method.

[0074] Amount of the detonation nanodiamonds in the plating solution is 0.005-15 g/l such as 0.01-10 g/l, preferably 0.01-3 g/l, more preferably 0.01-2 g/l, even more preferably 0.01-1 g/l, even more preferably 0.01-0.5 g/l and most preferably 0.01-0.1 g/l such as 0.05 g/l. With g/l of nanodiamonds in plating solution (electrolyte) is meant gram of diamond particles per litre of plating solution (electrolyte).

[0075] In one embodiment the detonation nanodiamonds exhibit zeta potential of at least +40 mV, preferably at least +45 mV, more preferably at least +50 mV measured with Laser Doppler Micro-Electrophoresis.

[0076] The plating solution may further comprise a reducing agent or several reducing agents. Examples of reducing agents are hypophosphite compounds, such as sodium hypophosphite and boron compounds such as sodium borohydride (NaBH.sub.4).

[0077] Amount of the reducing agent in the plating solution can be adjusted depending on the wanted properties of coating forming in the electroless metal plating process.

[0078] In one embodiment the plating solution may further comprise additional components such as stabilizers, surfactants, brighteners and/or pH adjusting agents. pH of the plating solution can be adjusted to any suitable pH value. In one embodiment the pH is adjusted to 3-6. Suitable pH adjusting agents are e.g. potassium carbonate, ammonium hydroxide and sulphuric acid.

[0079] The plating solution may also comprise particles that have effect on properties of final metal coating obtained by the electroless or electrolytic metal plating process. These particles can be soft or hard particles. The soft particles reduces friction coefficient of the coating but impair its abrasive wear and hardness properties. The hard particles enhance hardness and wear of the coating but impair coating friction properties. Examples of soft particles are graphite, graphene, carbon nanotubes, polytetrafluoroethylene (PTFE), hexagonal boron nitride, calcium fluoride and molybdenum disulphide (MoS.sub.2). Examples of hard particles are silicon carbide, diamond particles larger than 15 nm, aluminium oxide, silicon dioxide, boron carbide, chromium carbide, titanium carbide and tungsten carbide but also other solid particles. The plating solution may comprise both soft and hard particles such as PTFE and silicon carbide.

[0080] In one embodiment the plating solution is free of surfactants.

[0081] In a second aspect of the present invention there is provided a method for producing an electroless metal plating solution. Said provided metal plating solution can also be an electrolytic metal plating solution.

[0082] More particularly there is provided a method for producing the electroless or electrolytic metal plating solution described above comprising adding detonation nanodiamonds substantially free, preferably free, of negatively charged functionalities to a solution comprising at least one source of metal ions, and mixing the solution.

[0083] The detonation nanodiamonds are substantially free of negatively charged functionalities. By term substantially free of negatively charged functionalities is meant that the applied detonation nanodiamond material acid value is less than 5.0. The acid value can be measured by potentiometric titration.

[0084] In a preferred embodiment the detonation nanodiamonds are free of negatively charged functionalities, that is, the acid value is 0.

[0085] The detonation nanodiamonds substantially free of negatively charges functionalities can be added as dry powder to the solution comprising the at least one source of metal ions. Preferably the detonation nanodiamonds are added as an aqueous suspension, more preferably as an aqueous dispersion. With suspension is meant a nanodiamond suspension with particle size distribution D90 higher than 100 nm. With dispersion is meant a nanodiamond suspension with particle size distribution D90 higher at most 100 nm. By particle size distribution D90 is meant that 90% of the particles are smaller than given particle size, and 10% of particles are larger than given particle size.

[0086] In a preferred embodiment the detonation nanodiamonds are added as an aqueous dispersion free of surfactants.

[0087] In one embodiment the electrolyte is based on water. In another embodiment, the electrolyte is based on an ionic liquid. In the latter embodiment, the nanodiamond powder, suspension or dispersion can be added and mixed into ionic liquid, in one additional embodiment followed by evaporation of nanodiamond dispersion contained water or another solvent. The nanodiamond particles can be also added to ionic liquid prior addition of any other electrolyte components.

[0088] The nanodiamond powder, suspension or dispersion can be mixed to a ready electrolyte or to any of the components the electrolyte is manufactured from.

[0089] In one embodiment pH of the plating solution is adjusted to 0-14. Preferably the pH is adjusted to 3-6, more preferably 4-6, such as 5.

[0090] The mixing of the nanodiamonds into the solution, also referred to as an electrolyte, can be conducted with any suitable method. Examples of such methods are mechanical mixing such as magnetic stirring or ultrasonication. In a preferred embodiment ultrasonication is not used.

[0091] In a third aspect of the present invention there is provided an electroless plating method. Said provided metal plating method can also be an electrolytic metal plating method.

[0092] More particularly there is provided an electroless plating method comprising immersing a substrate into a plating bath comprising the electroless metal plating solution described above.

[0093] In one embodiment the substrate is immersed into the plating bath for 1-360 min, preferably 1-90 min, and most preferably 30-90 min. If manufacturing very thin metal coatings, the substrate can also be immersed to plating bath only for few seconds time. If manufacturing very thick coatings, or applying this method for electroforming purposes, the substrate can be immersed into the plating bath for longer periods of time, including those over 360 minutes.

[0094] In one embodiment temperature of the plating bath is 20-100 C., preferably 50-95 C., and more preferably 80-95 C. such as 90 C.

[0095] Deposition rate of the metal and nanodiamonds is dependent on various factors, such as phosphorus content of the bath, temperature of the bath, pH of the bath, activity of the bath, agitation and age of the bath.

[0096] The substrate can be any suitable substrate. The substrate can be a metal, an alloy, ceramic or a polymer material. In one embodiment the metal is selected from steel, copper, gold, iron, zinc, aluminum, cobalt, nickel, rhodium, palladium and platinum. Akrylenitrilebutadienestryrene (ABS) polymer is an example of suitable polymer.

[0097] The substrate can be pretreated before the immersing step. Such pretreatment methods include mechanical cleaning of the substrate i.e. sandblasting, solvent cleaning, hot degreasing and electrocleaning such as cathodic or anodic electrocleaning. The substrate can be subjected to one or several pretreatment methods. After pretreatment, the substrate may be rinsed with for example water. Surface of the substrate may also be activated after the pretreatment steps(s), before the immersing step. For example surface(s) of polymers are preferably activated before the plating.

[0098] In one embodiment the substrate is first underplated with a metal, optionally rinsed and then immersed into the plating bath comprising the electroless or electrolytic metal plating solution described above for producing a detonation nanodiamond containing metal layer as the outermost layer. Optionally, additional layer(s) can be plated on the detonation nanodiamond containing metal layer.

[0099] In one embodiment, during the electroless or electrolytic plating process pH, reducing agent concentration, metal concentration and detonation nanodiamond concentration are monitored and adjusted if necessary.

[0100] In one embodiment the electroless or electrolytic plating method further comprises after treatment step(s), such as rinsing, passivation and/or heat treatment of the formed metallic coating. Preferably the heat treatment is an annealing process. With the annealing process the crystal structure of the metallic coating is modified. The annealing is performed at elevated temperature of 100-1000 C., preferably 100-700 C. such as 400 C. for 15 min-2 hours such as 1 hour. The heat treatment temperature and time varies depending on the desired properties. Annealing can be conducted in air atmosphere or in reducing gas atmosphere such as 95% nitrogen and 5% hydrogen or air can be used. Also the use of inert gas can reduce oxidation of the plating.

[0101] In a fourth aspect of the present invention there is provided a metallic coating.

[0102] More particularly there is provided a metallic coating, preferably produced with above the process, comprising metal and detonation nanodiamonds, wherein the nanodiamonds are substantially free of negatively charged functionalities.

[0103] The detonation nanodiamonds are substantially free of negatively charged functionalities. By term substantially free of negatively charged functionalities is meant that the applied detonation nanodiamond material acid value is less than 5.0. The acid value can be measured by potentiometric titration.

[0104] In a preferred embodiment the detonation nanodiamonds are free of negatively charged functionalities, that is, the acid value is 0.

[0105] In one embodiment the metallic coating is produced with the method disclosed above.

[0106] Amount of the detonation nanodiamonds in the metallic coating is 0.01-4.0 wt. %, preferably 0.01-1.0 wt. %, and more preferably 0.01-0.5 wt. % such as 0.2 wt. % based on the total weight of the metallic coating.

[0107] In one embodiment the metallic coating has a thickness of 0.01-100 m, and more preferably 10-30 m, such as 25 m.

[0108] The metallic coating exhibits reduction in Taber wear index (TWI) compared to a metallic coating without detonation nanodiamonds. The reduction in TWI is at least 10%, preferably at least 50%, more preferably at least 100%, most preferably at least 200% compared to a coating without detonation nanodiamonds.

[0109] The metallic coating coefficient of friction is not increased by more than 15%, as compared to coating without detonation nanodiamond additives.

[0110] The metallic coating corrosion resistance, as measured by neutral salt spray test, is not reduced by more than 5 R.sub.P units, as compared to coating without nanodiamond additives. What is meant by neutral salt spray test is that steel substrates are plated with a metallic coating of certain material and application related thickness and exposed to 5 wt. % NaCl vapour for a predetermined period of time. The samples are being evaluated for their ability to prevent the steel from rusting. The more detailed description of the test procedure and apparatuses are explained in ASTMB117, EN ISO 9227:2012 and EN ISO 10289:2001 standards.

[0111] The metallic coating can be subjected to heat treating, preferably annealing. Such heat treated, preferably annealed, coating exhibits preferably more than 100%, more preferably more than 200% and most preferably more than 300% as reduction in TWI, as compared to metallic coating without detonation nanodiamonds.

[0112] The above defined detonation nanodiamonds can also be utilized in electrolytic plating methods. When introducing detonation nanodiamonds substantially free, preferably free, of negatively charged functionalities into an electro metal plating solution, tribological properties, such as wear and hardness and corrosion resistance, of formed metal coating are improved significantly compared to coatings not having detonation nanodiamonds.

[0113] The electrolytic (also referred to as electro) metal plating solution comprises at least one source of metal ions and detonation nanodiamonds, wherein the detonation nanodiamonds are substantially free of negatively charged functionalities.

[0114] The detonation nanodiamonds are substantially free of negatively charged functionalities. By term substantially free of negatively charged functionalities is meant that the applied detonation nanodiamond material acid value is less than 5.0. The acid value can be measured by potentiometric titration.

[0115] In a preferred embodiment the detonation nanodiamonds are free of negatively charged functionalities, that is, the acid value is 0. This presence of acidic surface functionalities can be determined by for example potentiometric titration or Boehm titration.

[0116] Examples of functionalities on detonation nanodiamond that are not negatively charged are hydrogen, amine and hydroxyl termination. Such detonation nanodiamonds are commercially available. In one preferred embodiment the detonation nanodiamond is functionalized with hydrogen and/or amine functionalities.

[0117] In one embodiment the electrolytic metal plating solution further comprises acid. Examples of suitable acids are sulphuric formic, acetic, citric, tartaric and lactic acid.

[0118] In other embodiment the electrolytic metal plating solution further comprises suitable basic additive or additives. Examples of suitable bases include but are not limited to ammonium hydroxide and sodium hydroxide.

[0119] Examples of chrome metal based electrolytes are hexavalent chrome (Cr.sup.6+) and trivalent chromium (Cr.sup.3+). Chromium trioxide is a typical source of hexavalent chrome. Chromium sulphate or chromium chloride are typical sources of trivalent chromium. It is possible to electroplate a large number of other pure metals but also their alloys comprised of two or more metals. The metals and metalloids that can be deposited electrolytically include Mn, Fe, Co, Ni, Cu, Zn, As, Se, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Re, Os, Ir, Pt, Au, Hg, Tl, Pb and Bi. The typical industrial electroplated wear and corrosion resistant coatings include hard chrome, decorative chrome and various nickel coatings. Hard chrome, also known as hexavalent chrome (Cr.sup.6+) uses chromium trioxide (also known as chromic anhydride) as the main ingredient. Hard chrome can be applied on metal substrates (typical base metals include steel, copper, alloys or aluminium) but also on plastics and ceramics. Its properties include remarkable wear resistance, hardness and low friction properties. Its main applications can be found within oil & gas industries, automotive and aerospace industries and on various industrial machinery parts. The typical coating thickness is 10-50 microns but can be as thick as 500 microns, for example in US produced car shock absorbers.

[0120] Amount of the detonation nanodiamonds in the electroplating solution is 0.005-15 g/l, preferably 0.01-3 g/l, more preferably 0.01-2 g/l, even more preferably 0.01-1 g/l, even more preferably 0.01-0.5 g/l and most preferably 0.01-0.1 g/l, such as 0.1 g/l.

[0121] The electrolytic plating solution may further comprise additional components such as stabilizers, surfactants, complexing agents, conductive salts, mist suppressants, brighteners, pH buffers and/or pH adjusting agents.

[0122] A method for producing an electrolytic plating solution comprises adding of detonation nanodiamonds substantially free, preferably fee, of negatively charged functionalities to a solution comprising at least one source of metal ions, and mixing the solution.

[0123] The detonation nanodiamonds substantially free of negatively charges functionalities can be added as dry powder to the solution comprising the at least one source of metal ions and acid. Preferably the detonation nanodiamonds are added as an aqueous suspension, more preferably as an aqueous dispersion.

[0124] In a preferred embodiment the detonation nanodiamonds are added as an aqueous dispersion free of surfactants.

[0125] In one embodiment pH of the electro plating solution is adjusted before addition of the detonation nanodiamonds.

[0126] The mixing can be conducted with any suitable method. Examples of such methods are magnetic stirring or ultrasonication. In a preferred embodiment ultrasonication is not used.

[0127] The substrate can be pretreated before the immersing step. Such pretreatment methods are mechanical cleaning of the substrate i.e. sandblasting, solvent cleaning, hot degreasing, electrocleaning and reverse etching. The substrate can be subjected to one or several pretreatment methods. After a pretreatment method the substrate may be rinsed with for example water. Surface of the substrate may also be activated after the pretreatment steps(s), before the immersing step. For example surface(s) of polymers are preferably activated before the plating.

[0128] In one embodiment the substrate is first underplated with a metal, optionally rinsed and then immersed into the plating bath comprising the electroless metal plating solution described above for producing a detonation nanodiamond containing metal layer as the outermost layer. Optionally another layer(s) can be plated on the detonation nanodiamond containing metal layer.

[0129] An example on electroplating method comprises steps: [0130] i) activating surface of a substrate [0131] ii) optionally rinsing the activated surface of the substrate [0132] iii) immersing the activated substrate into a electro plating bath comprising the electro plating solution defined above and applying an electric current [0133] iv) optionally rinsing at least once the electro plated substrate.

[0134] In a preferred embodiment the optional rinsings of steps ii) and iv) are performed.

[0135] The substrate can be pretreated before the activation step. Such pretreatment methods are mechanical cleaning of the substrate i.e. sandblasting, solvent cleaning, hot degreasing and electrocleaning. The substrate can be subjected to one or several pretreatment methods. After a pretreatment method the substrate may be rinsed with for example water.

[0136] In one embodiment the substrate is first underplated with a metal, optionally rinsed and then immersed into the electro plating bath comprising the electro plating solution defined above for producing a detonation nanodiamond containing metal layer as the outermost layer. Optionally another layer(s) can be plated on the detonation nanodiamond containing metal layer.

[0137] The substrate can be any suitable substrate. The substrate can be a metal such as steel, copper, aluminium, an alloy, ceramic or a polymer material, preferably steel, copper or aluminium.

[0138] The activation of the surface of the substrate may be conducted in an activation bath. In one embodiment the activation bath comprises acid such as sulphuric acid or chromic acid. In one exemplary embodiment the activation bath comprises chromic acid and with a reverse current is run through it. This etches the substrate surface and removes any scale.

[0139] In one embodiment the activation step is done in the electro plating bath comprising the electro plating solution defined above.

[0140] The electric current in step iii) may be direct current or alternating current, or the current can be altered to be first direct current and then alternating current, or first alternating current and then direct current. The current can be switched on and off during the plating process.

[0141] In one embodiment current density, during the electroplating step iii), is between 10-130 amps per square decimetre.

[0142] In the electroplating step iii) the substrate may be immersed in the bath for 5-90 seconds.

[0143] In one embodiment temperature of the electroplating bath is 20-70 C.

[0144] The electroplated substrate may be rinsed at least once, and optionally dried or passivated.

[0145] In one embodiment, during the electro plating process pH, metal concentration and detonation nanodiamond concentration are monitored and adjusted if necessary.

[0146] In one embodiment hexavalent chrome, also known as hard chrome is plated on a substrate. The hexavalent chrome (Cr.sup.6+) uses chromium trioxide (also known as chromic acid anhydride) as the main ingredient. Typical coating thickness is 10-50 microns but can be as thick as 500 microns. In an exemplary embodiment hexavalent chromium plating process comprises process steps: (a) activation, (c) electro plating, (d) at least one rinsing. The activation bath is preferably a tank of chromic acid with a reverse current run through it. This etches the substrate surface and removes any scale. In one embodiment the activation step is done in chromium bath (electro plating bath). The chromium bath comprises chromium trioxide (CrO.sub.3) and sulphuric acid, the ratio of which varies between 75:1 to 250:1 by weight, and additionally the detonation nanodiamonds. This results in an acidic bath having pH of 0. Temperature and current density in the bath affect the brightness and final coverage. For hard coating temperature ranges from 40 to 75 C. Temperature is also dependent on the current density, because a higher current density requires a higher temperature. The bath is optionally agitated to keep the temperature steady and achieve a uniform deposition. After the plating process in the chromium bath, the plated substrate having the coating is rinsed at least once.

[0147] In one embodiment trivalent chromium is deposited on a substrate The trivalent chromium plating, also known as tri-chrome, Cr.sup.3+, and chrome (III) plating, uses chromium sulphate or chromium chloride as the main component. A trivalent chromium plating process is similar to the hexavalent chromium plating process, except for the bath chemistry and anode composition. In one embodiment the bath is a chloride- or sulphate-based electrolyte comprising also sulphuric acid and the detonation nanodiamonds using graphite or composite anodes, and additionally additives to prevent oxidation of trivalent chromium to the anodes. In other embodiment the bath is a sulphate-based bath comprising also sulphuric acid and the detonation nanodiamonds that uses lead anodes surrounded by boxes filled with sulphuric acid (known as shielded anodes), which keeps the trivalent chromium from oxidizing at the anodes. Yet in another embodiment the bath is a sulphate-based bath comprising also sulphuric acid and the detonation nanodiamonds that uses insoluble catalytic anodes, which maintains an electrode potential that prevents oxidation. The trivalent chromium-plating process can plate the work-pieces at a similar temperature, rate and hardness, as compared to hexavalent chromium. In one embodiment the plating temperature ranges from 30 to 50 C. Trivalent chrome typical coating thickness ranges from 0.10 to 1.30 m but can be currently extended to 10 micron thicknesses. In order to replace hexavalent chrome in most of the industrial applications, the coating thickness should reach 100 microns, and in dedicated applications thicknesses beyond 500 microns.

[0148] In one embodiment the electroplating method further comprises a step of heat treating the formed metallic coating. Preferably the heat treatment is an annealing process. With the annealing process the crystal structure of the metallic coating is modified. The annealing is performed at elevated temperature of 100-1300 C. such as 400 C. for 15 min-24 hours such as 1 hour. The heat treatment temperature and time varies depending on the desired properties. Annealing can be conducted in air atmosphere or reducing gas such as 95% nitrogen and 5% hydrogen or air can be used. Also the use of inert gas can reduce oxidation of the plating.

[0149] In one embodiment the nickel composite coating uses nickel sulphate as its main component, boric acid as pH buffer and proprietary additives to stabilize the bath. The plating temperature can be preferably between 40-50 C., more preferably between 43-47 C., such as 45 C. The plating current can vary between 1-40 A/dm.sup.2.

[0150] The metallic coating, preferably produced with the above defined electroplating method, comprises metal and detonation nanodiamonds, wherein the nanodiamonds are substantially free, preferably free, of negatively charged functionalities.

[0151] Amount of the detonation nanodiamonds in the metallic coating is 0.01-4.0 wt. %, preferably 0.01-1.5 wt. %, more preferably 0.01-0.5 wt. %, and even more preferably 0.01-0.4 wt. % such as 0.2 wt. % based on the total weight of the metallic coating.

[0152] Thickness of the metallic coating depends on the deposited metal and process conditions. Coating with noble metal can be up to 0.2 m, and coatings with chrome can be up to few-several mm.

[0153] The metallic coating exhibits reduction in Taber wear index (TWI) compared to a metallic coating without detonation nanodiamonds. The reduction in TWI is at least 50%, preferably at least 100%, more preferably at least 200% compared to a coating without detonation nanodiamonds.

[0154] The metallic coating can be subjected to heat treating, preferably annealing. Such heat treated coating exhibits preferably more than 100%, more preferably more than 200% and most preferably more than 300% as reduction in TWI, as compared to metallic coating without detonation nanodiamonds.

[0155] In the following the invention will be described in more detail by means of examples. The purpose of the examples is not to restrict the scope of the claims.

EXAMPLES

Apparatuses and Materials

[0156] Ultrasonic device: Hielscher UP400S from company Hielscher GmbH. Sonicator tip H22.

[0157] Annealing furnace: KERAKO tube furnace from company Keracomp Oy.

[0158] Annealing protective gas: Argon.

[0159] Ball on disk device: CSM Instrument Tribometer from Company CSM Instruments SA. Measurements were conducted University of Eastern Finland, Joensuu, Finland and at Danmarks Teknologisk Universitet, Kgs. Lyngby, Denmark.

[0160] Glow discharge optical emission spectroscopy device: Spectrum Analytic GDA 750 from company Spectruma Analytic Inc. The measurements were conducted at University of Oulu, Oulu, Finland.

[0161] Microhardness tester: Future-Tech FM-700 from company Future-Tech Corp. The measurements were conducted at Danmarks Teknologisk Universitet, Kgs. Lyngby, Denmark.

[0162] Wear resistance tester: Taber Rotary Abraser 5135 from company Taber Instruments Corporation. The measurements were conducted at Carbodeon's laboratory, Vantaa, Finland.

[0163] Salt spray chamber: Q-FOG CCT-1100. The measurements were conducted at Metropolia School of Applied Sciences, Vantaa, Finland. Substrate material for salt spray testing: CR4 steel plates from Company Erichsen, the plates aree in accordance with ISO 3574, for organic coatings in accordance with DIN EN ISO 9227.

[0164] Scale: Sartorius CPA324S from Company Sartorius.

[0165] Scanning electron microscope: Jeol JSM 5900 from Company JEOL. Imaging was conducted at Danmarks Teknologisk Universitet, Kgs. Lyngby, Denmark.

[0166] Tunneling electron microscope: Tecnai Spirit G2 from Company FEI

[0167] Abrasive wheels: CS-10 from company Taber Instruments Corporation.

[0168] Refacing discs: S-11 from company Taber Instruments Corporation.

[0169] Substrate material: Oxygen free copper (CW008).

[0170] Electrocleaning bath: Uniclean 251 from Company Atotech GmbH.

[0171] Activation bath: Uniclean 675 from Company Atotech GmbH.

[0172] Bright nickel electrolyte: Supreme Plus from Company Atotech GmbH.

[0173] Electroless nickel bath: Nichem 1122 from Company Atotech GmbH.

[0174] Electrolytic nickel plating bath: Scanimet from Company Atotech GmbH.

[0175] Silicon carbide particles: Scanimet silicon carbide.

[0176] Applied detonation nanodiamond additives:

[0177] Hydrogen D is hydrogen functionalized detonation nanodiamond, available in its aquous dispersion form but also in a range of polar organic solvents. Hydrogen D contained nanodiamonds are also available as powder grade product, under product name Hydrogen P. Hydrogen D and P products are commercially available from Carbodeon Ltd Oy, Finland. Hydrogen P and D products exhibit highly positive zeta potential, the commercial products exhibiting minimum +50 mV zetapotential. The aquous nanodiamond dispersion is agglomeration-free at pH 3 to 9 and exhibits higher positive zeta potential also at very acidic conditions than for example Carbodeon commercial nanodiamond dispersion uDiamond Andante. Hydrogen D in water nanodiamond concentration is 2.5 wt. %, i.e. one liter of Hydrogen D nanodiamond dispersion contains 25 grams of nanodiamond particles.

[0178] Amine D is amine functionalized detonation nanodiamond, available in its aquous dispersion form but also in a range of polar organic solvents. Amine D contained nanodiamonds are also available as powder grade product, under product name Amine P. Amine D and P products are commercially available from Carbodeon Ltd Oy, Finland. Amine P and Amine D products exhibit highly positive zeta potential, the commercial products exhibiting minimum +50 mV zeta potential. Amine D in water nanodiamond concentration is 0.5 wt. %, i.e. one liter of Amine D nanodiamond dispersion contains 5 grams of nanodiamond particles.

[0179] Vox D is carboxyl functionalized detonation nanodiamond, available in its aquous dispersion form but also in a range of polar organic solvents. Vox D contained nanodiamonds are also available as powder grade product, under product name Vox P. Vox D and P products are commercially available from Carbodeon Ltd Oy, Finland. Vox P and Vox D products exhibit highly negative zeta potential, the commercial products exhibiting minimum 50 mV zeta potential. The aquous nanodiamond dispersion is agglomeration-free at pH 5 to 12. Vox D in water nanodiamond concentration is 5.0 wt. %, i.e. one liter of Vox D nanodiamond dispersion contains 50 grams of nanodiamond particles.

[0180] The applied detonation nanodiamond material can be which ever detonation nanodiamond material exhibiting acid value less than 5.0. Commercial detonation nanodiamond dispersion uDiamond Andante acid value is 5.0 and its introduction effiicient introduction to applied metal electrolytes requires the use of ultrasonication. Moreover, the surface contained acidic functions, including carboxylic acid functionalities, cause flocculation of electrolyte contained metal ions. The aquoues Andante detonation nanodiamond additive is is agglomeration-free at pH 3 to 6. The uDiamond Andante nanodiamond concentration is 5 wt. %, i.e. one liter of Andante nanodiamond dispersion contains 50 grams of nanodiamond particles. The acid value can be measured by potentiometric titration.

Measurement of Detonation Nanodiamond Acid Values by Potentiometric Titration

[0181] The detonation nanodiamond powder and dispersion acid values can be measured by potentiometric titration which process includes the next steps: Every sample measurement was conducted twice, with a sample size of 1.5 g per titration. The titrations were carried out with automated Metrohm titrator. Determination of acid functions: Solid samples were weighted accurately (1.5 g). The prepared samples were dispersed into 75 ml of neutralized ethanol (water content 0.5 wt. %), using Hielscher 400 W ultrasonic unit. The prepared samples were titrated with 0.1 M KOH (in methanol), using phenoliftalene as an indicator. The samples were treated continuously with Argon gas flow during the titration. The titration end point was detected by using an indicator and with potentiometric means, using Methrohm Solvotrode electrode and drawing a titration curve. The acid value is determined as milligram amount of KOH (potassium hydroxide) required neutralize the acidic functionalities in 1 g of nanodiamond material. The measurement can be interfered by aqueous phase contained various carbonates and thus, measure values higher than the studied detonation nanodiamond samples would exhibit.

[0182] The studied carboxylated nanodiamond powder sample, known also as Vox P product exhibited an acid value of 34.7. The studied carboxylated nanodiamond aqueous dispersion sample, known also as Vox D in water product exhibited an acid value of 30.2.

[0183] The studied hydrogenated nanodiamond powder sample, known also as Hydrogen P product exhibited an acid value of 1.3. The studied hydrogenated nanodiamond aqueous dispersion sample, known also as Hydrogen D in water product exhibited an acid value of 1.8.

[0184] The studied amine-terminated nanodiamond powder sample, known also as Amine P product exhibited an acid value of 3.0. The studied hydrogenated nanodiamond aqueous dispersion sample, known also as Amine D in water product exhibited an acid value of 3.1.

Boehm Titration to Determine Detonation Nanodiamond Surface Contained Acidic Functional Groups

[0185] The general method:

[0186] 1.5 g of detonation nanodiamond powder is mixed into 50 ml (V.sub.B) of 0.05 M (c.sub.B) NaHCO.sub.3 solution. The mixture is shaken for 24 hours to let the base neutralize all of the surface carboxyl groups of the nanodiamonds. Solution is then centrifuged for 30 minutes with relative centrifugal force (RCF) of 8240. Further, solution is filtered through a 0.8 m membrane to extract all the diamond particles. A back-titration method is used to determine the amount of NaHCO.sub.3 molecules that have been neutralized by the carboxyl groups. In order to execute the back-titration, 10 ml (V.sub.a) of the filtered sample is neutralized with 20 ml of 0.05 M HCl solution. This new mixture is degassed for 2 hours with argon flux through the sample, to avoid the error caused by dissolved CO.sub.2. The degassed sample is finally titrated with 0.05 M NaOH solution. Since HCl is a strong base and NaOH is a strong acid the equivalent point of the titration is set to be 7.00.

[0187] For the back-titration the amount of the carboxyl groups can be determined by:

[00001]$n_{\mathrm{CSF}}=\frac{n_{\mathrm{HCl}}}{n_B}.Math.c_B.Math.V_B-\frac{V_B}{V_a}.Math.\left(c_{\mathrm{HCl}}.Math.V_{\mathrm{HCl}}-c_{\mathrm{NaOH}}.Math.V_{\mathrm{NaOH}}\right)$

Where n.sub.CSF stands for the amount of the carbon surface functionalities, c.sub.B and V.sub.b are the concentration and volume of the base mixed with the diamond powder, and V.sub.a is the volume of the sample neutralized with the HCl solution. Ratio n.sub.HCl/n.sub.B is the stoichiometric factor of the reaction chemistry, in sodium bicarbonate's case it equals 1. The resulting n.sub.CSF is further divided by the carbon material mass, thus the unit of the result will be mol/g.

Hydrogen P Detonation Nanodiamond Powder:

[0188] Boehm titration method was applied to measure the amount of acidic groups on Carbodeon's uDiamond Hydrogen P detonation powder. The determined result was 73.9 mol/g. The negative result can be explained by the fact that when Hydrogen P nanodiamond powder is mixed with water, the slurry is basic (pH>7). The Hydrogen P powder by itself increases the amount of hydroxyl groups that need to be neutralized by HCl in the back-titration. Thus the result is negative and it can be concluded that Hydrogen P nanodiamond powder is free from carboxylic groups.

Preparation of Detonation Nanodiamond Containing Electroless Nickel Electrolyte Using Ultrasonic Mixing

[0189] The electroless nickel electrolyte (electroless nickel plating solution) was prepared according to the supplier's instructions. The pH of the electrolyte was adjusted to 5 and was left to stir overnight in order to stabilize the bath.

[0190] 1 litre of room temperature electrolyte was taken into 2 litre beaker. Detonation nanodiamond dispersion was pipetted into electrolyte and ultrasonic mixing was performed for 10 minutes with full power. This procedure was repeated 5 times in order to make 5 litres of detonation nanodiamond containing electrolyte.

Preparation of Detonation Nanodiamond Containing Electroless Nickel Electrolyte Using Ultrasonic Mixing

[0191] The electroless nickel electrolyte (electroless nickel plating solution) was prepared according to the suppliers instructions. The pH of the electrolyte was adjusted to 5 and was left to stir overnight in order to stabilize the bath.

[0192] 1 litre of room temperature electrolyte was taken into 2 litre beaker. Detonation nanodiamond dispersion was pipetted into electrolyte and ultrasonic mixing was performed for 10 minutes with full power. This procedure was repeated 5 times in order to make 5 litres of detonation nanodiamond containing electrolyte.

Preparation of Detonation Nanodiamond Containing Electroless Nickel Electrolyte without Ultrasonic Mixing

[0193] The electroless nickel electrolyte (electroless nickel plating solution) was prepared according to the supplier's instructions. The pH of the electrolyte was adjusted to 5 and the resulting electrolyte was left to stir overnight in order to stabilize the bath.

[0194] The desired amount of detonation nanodiamonds was measured into small beaker and diluted with 250 ml of DI-water and stirred gently. This diluted dispersion was added into the electroless nickel bath and left to mix using magnetic stirring for 15 minutes before heating the bath to operation temperature.

Preparation of Detonation Nanodiamond Containing Electrolytic Nickel Electrolyte Using Ultrasonic Mixing

[0195] The electrolytic nickel electrolyte was prepared so that first 500 g/l of Scanimet Nickel salt NiSO.sub.4(H.sub.2O).sub.6 was dissolved into DI-water. Then 40 g/l of Boric acid was dissolved and finally 16.5 ml/l of Scanimet TA additive was added and mixed thoroughly. Detonation nanodiamond dispersion was pipetted into electrolyte and ultrasonic mixing was performed for 10 minutes. Silicon carbide particles that were also tested were not sonicated once added.

Plating Procedure for Electroless Nickel Samples

[0196] The plating of the samples was done according to process route described below:

[0197] Cathodic electrocleaning 20 s, 2 A/dm.sup.2->2 rinses with DI-water->Activation 20 s, room temperature->rinse with DI-water->Bright nickel strike 90 s, 55 C., 4 A/dm.sup.2->2 rinses with DI-water->Activation 20 s->rinse->Electroless nickel plating 1 hour, 89 C.1 C.

[0198] The pH and the nickel concentration of the electrolyte were monitored and adjusted according to the manufacturer's instruction and were held within the limits set by the manufacturer.

Plating Procedure for Electrolytic Nickel Samples

[0199] The copper plates were degreased cathodically for 3 minutes, activated in DeWeKa dry acid and electroplated in nickel SLOTONIK 40 at a current density of 3.5 A/dm.sup.2 at 55 C. with stirring for 11.5 minutes.

[0200] The electrolytic nickel-nanodiamond composite was plated using 30 A/dm.sup.2 current density and plated for 30 minutes.

Heat Treatment Procedure (Annealing)

[0201] Heat treatment was performed at 400 C. for 1 hour under argon atmosphere to prevent oxidation of the nickel coating. The heat treatment temperature and time can vary depending on the desired properties. It is well known for anyone skilled in the art that electroless nickel phosphorous form partly amorphous coating that's crystallinity can be modified using heat treatment process. It is also known that the protective gas can also be reducing gas such as 95% nitrogen and 5% hydrogen, or air can also be used.

Wear Resistance Measurements

[0202] Wear resistance measurements were conducted using Taber abraser 5135 rotary abraser. CS-10 abrasive rollers with 1 kg weight were used. The test length was 6000 revolutions, and the substrate was measured every 1000 revolutions. Average weight loss in mg per 1000 revolutions (excluding the first 1000 revolutions) is the Taber Wear Index of the plating. After every 1000 revolutions the abrasive rollers were resurfaced. The test follows ASTM B733 standard but differs in coating thickness and substrate material.

Microhardness Measurements

[0203] Vickers microhardness measurements were conducted using Future-Tech FM-700 microhardness tester with 10 gram load.

Determination of Carbon Content in the Coating

[0204] The carbon (diamond) content measurements were conducted at University of Oulu, Finland, using glow discharge optical emission spectroscopy (GDOES) which gives the carbon content throughout the coating thickness.

Example 1

[0205] Nanodiamond Hydrogen D in water was dispersed into electrolyte using ultrasonic mixing in concentrations 0.05 g/l and 0.1 g/l (as calcutalted in nanodiamond concentration) and plated using the abovementioned route. With 0.05 g/l is meant 0.05 grams of nanodiamond particles in one liter of electrolyte. With 0.1 g/l is meant 0.1 grams of nanodiamond particles in one liter of electrolyte. Both annealed an as-plated samples were tested for their wear resistance. Results are presented in Table 1. The panel plated with 0.05 g/l of Hydroged D contained nanodiamond particles gave 216% improved wear resistance and the panel plated with 0.1 g/l of Hydrogen D contained nanodiamond particles gave 252% improved wear resistance, as compared to reference sample plated without Hydrogen D nanodiamond additive. The annealed panel with 0.05 g/l of Hydrogen D contained nanodiamond particles gave 296% improvement in coating wear resistance. The annealed panel with 0.1 g/l of Hydrogen D contained nanodiamond particles gave 346% improvement in coating wear resistance, as compared to annealed reference sample plated without Hydrogen D nanodiamond additive.

TABLE-US-00001 TABLE 1 TWI, as-plated TWI, annealed Hydrogen D 0.05 g/l 5.8 2.7 Hydrogen D 0.1 g/l 5.2 2.4

Example 2

[0206] Nanodiamond Amine D in water was dispersed into electrolyte using ultrasonic mixing in concentrations 0.05 g/l and 0.1 g/l (as calcutalted in nanodiamond concentration) and plated using the abovementioned route. both annealed an as-plated samples were tested for their wear resistance. Results are presented in Table 2. The panel plated with 0.05 g/l of Amine D contained nanodiamond particles gave 195% improved wear resistance and the panel plated with 0.1 g/l of Amine D contained nanodiamond particles gave 216% improved wear resistance, as compared to reference sample plated without Amine D nanodiamond additive. The annealed panel with 0.05 g/l of Amine D contained nanodiamond particles gave 282% improvement in coating wear resistance. The annealed panel with 0.1 g/l of Amine D contained nanodiamond particles gave 406% improvement in coating wear resistance, as compared to annealed reference sample plated without Amine D nanodiamond additive.

TABLE-US-00002 TABLE 2 TWI, as-plated TWI, annealed Amine D 0.05 g/l 6.2 2.8 Amine D 0.1 g/l 5.8 2.1

Example 3

Reference

[0207] Nanodiamond dispersion Vox D in water was dispersed into electrolyte using ultrasonic mixing in concentration 0.05 g/l (as calculated in nanodiamond concentration) and plated using the abovementioned route. The as-plated samples were tested for their wear resistance. Results are presented in Table 3. The result clearly demonstrates the nanodiamond surface contained carboxylic acid and other acidic functions impairing effect on coating wear resistance properties. The panel plated with 0.05 g/l of Vox D contained nanodiamonds gave only 49% improvement in wear resistance, which result is well in line with published data but with significantly higher nanodiamond concentrations.

TABLE-US-00003 TABLE 3 TWI, as-plated Vox D 0.05 g/l 12.3

Example 4

[0208] Nanodiamond Hydrogen D was dispersed into electrolyte without using ultrasonic mixing in concentration 0.1 g/l (as calcutalted in nanodiamond concentration) and plated using the abovementioned route. Both annealed an as-plated samples were tested for their wear resistance. The panel plated with 0.1 g/l of Hydrogen D contained nanodiamond particles gave 221% improved wear resistance, as compared to reference sample plated without Hydrogen D nanodiamond additive. The annealed panel with 0.1 g/l of Hydrogen D contained nanodiamond particles gave 312% improvement in coating wear resistance, as compared to annealed reference sample plated without Hydrogen D nanodiamond additive. Results are presented in Table 4. The result clearly indicates there is no need for using ultrasonication for getting the nanodiamonds dispersed into electrolyte but the similar performance can also be reached without ultrasonication step.

TABLE-US-00004 TABLE 4 TWI as-plated TWI annealed Hydrogen D 0.1 g/l 5.7 2.6

Example 5

[0209] Nanodiamond Amine D was dispersed into electrolyte without using ultrasonic mixing in concentrations 0.05 g/l and 0.1 g/l (as calcutalted in nanodiamond concentration) and plated using the abovementioned route. Both annealed an as-plated samples were tested for their wear resistance. The panel plated with 0.1 g/l of Amine D contained nanodiamond particles gave 190% improved wear resistance, as compared to reference sample plated without Amine D nanodiamond additive. The annealed panel with 0.05 g/l of Amine D contained nanodiamond particles gave 157% improvement in coating wear resistance. The annealed panel with 0.1 g/l of Amine D contained nanodiamond particles gave 365% improvement in coating wear resistance, as compared to annealed reference sample plated without Amine D nanodiamond additive. Results are presented in Table 5.

TABLE-US-00005 TABLE 5 TWI as-plated TWI annealed Amine D 0.05 g/l 3 Amine D 0.1 g/l 6.3 2.3

Example 6

Reference

[0210] Reference samples were plated using the abovementioned route, however the plating solution did not contain any nanodiamonds. Both annealed an as-plated samples were tested for their wear resistance. Results are presented in Table 6.

TABLE-US-00006 TABLE 6 TWI as-plated TWI annealed Reference 18.3 10.7

[0211] As can be seen from the tables 1-6, the samples according to the present invention gave better TWI results than the Reference samples. The improvements are even more pronounced within the annealed samples.

Carbon Content Analyses

[0212] The carbon content was measured using glow discharge optical spectroscopy method. The carbon analysis results are presented in Table 7. By sonicated is meant ultrasonic tool was applied during introduction of nanodiamonds into electrolyte. Ultrasonication was not applied during actual sample plating. By unsonicated is meant no ultrasonic tools were applied during introduction of nanodiamonds to the electrolyte, nor during sample plating.

TABLE-US-00007 TABLE 7 Sample Carbon content [wt-%] Hydrogen D 0.05 g/l sonicated 0.15 Hydrogen D 0.1 g/l sonicated 0.28 Hydrogen D 0.1 g/l unsonicated 0.28 Amine D 0.1 g/l unsonicated - sample 1 0.22 Amine D 0.1 g/l unsonicated - sample 2 0.16

Friction Coefficient Measurement Results

[0213] Friction coefficient measurements were conducted with ball on disk method. Samples were plated and the friction coefficient was measured against Al.sub.2O.sub.3 and hardened steel ball. Temperature in which the measurements were conducted was 241 C. The applied force was 2N and the rotation speed was 5 cm/s. The results are presented in FIGS. 1-3.

[0214] FIG. 1 presents friction coefficients of as-plated samples according to the present invention and reference against Al.sub.2O.sub.3.

[0215] FIG. 2 presents friction coefficients of samples according to the present invention and reference annealed in 400 C. for 1 hour against Al.sub.2O.sub.3.

[0216] FIG. 3 presents friction coefficients of samples according to the present invention and reference annealed in 400 C. for 1 hour against steel.

[0217] As can be seen from the FIGS. 1-3 the plated samples according to the present invention gave resulted in lower coefficient of friction than the reference samples.

Corrosion Resistance Measurements

[0218] The corrosion resistance of plated electroless nickel samples measured with neutral salt spray (96 hours). The plating was deposited on Erichsen steel panels to a thickness of 25.4 m2 m. The plating was conducted in a following manner:

[0219] Ethanol cleaning of the substrate, rinse, anodic electrocleaningUniclean 251 4 A/dm2 120 s, 2 rinses, activationUniclean 675 20 s, 2 rinses, electroless nickel platingAtotech Nichem 1122 to 25.4 m.

[0220] The prepared samples were visually inspected for their ability to protect the steel layer (formation of red rust). After 96 hours the samples were rinsed with tap water and dried with pressurized air. The results of the tests are presented in Table 8.

TABLE-US-00008 TABLE 8 Corrosion protection ability of electroless nickel coatings with and without nanodiamonds. Sample Thickness [m] Rp-value Reference, annealed 24.3 9 Reference, annealed 25.8 9 Reference, as-plated 26.1 9 Reference, as-plated 25.5 9 Amine D, 0.1 g/l, no sonication, annealed 24.7 9 Amine D, 0.1 g/l, no sonication, annealed 25.1 9 Amine D, 0.1 g/l, no sonication, annealed 24.5 9 Hydrogen D, 0.1 g/l, no sonication, annealed 26.7 9 Hydrogen D, 0.1 g/l, no sonication, annealed 26.4 9 Hydrogen D, 0.1 g/l, no sonication, annealed 23.0 9 Hydrogen D, 0.1 g/l, no sonication, annealed 26.8 9 Hydrogen D, 0.05 g/l, ultrasonicated, 23.7 9 annealed Hydrogen D, 0.05 g/l, ultrasonicated, 24.7 9 annealed Hydrogen D, 0.05 g/l, ultrasonicated, 23.7 8 annealed Hydrogen D, 0.05 g/l, ultrasonicated, 25.6 8 as-plated Hydrogen D, 0.05 g/l, ultrasonicated, 25.7 8 as-plated Hydrogen D, 0.05 g/l, ultrasonicated, 27.3 8 as-plated Hydrogen D, 0.05 g/l, ultrasonicated, 27.2 8 as-plated Hydrogen D, 0.05 g/l, ultrasonicated, 24.6 8 annealed Hydrogen D, 0.1 g/l, ultrasonicated, 24.5 8 annealed Hydrogen D, 0.1 g/l, ultrasonicated, 8 as-plated Hydrogen D, 0.1 g/l, ultrasonicated, 8 as-plated Hydrogen D, 0.1 g/l, ultrasonicated, 8 as-plated Hydrogen D, 0.1 g/l, ultrasonicated, 8 as-plated Hydrogen D, 0.1 g/l, no sonication, 24.3 8 as-plated Amine D, 0.1 g/l, no sonication, as-plated 25.8 8 Amine D, 0.1 g/l, no sonication, as-plated 24.2 8 Amine D, 0.1 g/l, no sonication, as-plated 24.2 8 Amine D, 0.1 g/l, no sonication, annealed 24.8 8 Hydrogen D, 0.1 g/l, no sonication, as-plated 23.7 7 Hydrogen D, 0.1 g/l, no sonication, as-plated 24.2 7 Amine D, 0.1 g/l, no sonication, as-plated 26.0 7 Hydrogen D, 0.1 g/l, no sonication, as-plated 23.7 6

Example 7

Electrolytic Nickel

[0221] Nanodiamond Hydrogen D was dispersed into the bath as stated above in concentrations 0.01 g/l, 1 g/l and 7.5 g/l (as calcutalted in nanodiamond concentration). Silicon carbide particle concentration in SiC-bath was 40 g/l and reference Ni contained neither particles. All baths were plated using 30 A/dm.sup.2 for 30 minutes. Plating was conducted in beaker using platinized Titanium web as anode.

[0222] FIG. 4 shows friction coefficients for all samples against Al.sub.2O.sub.3 ball. The length of the test was 500 meters, the force used was 10N and the speed was 10 cm/s. From FIG. 4 it can be seen that all ND-composite coatings exhibit better wear resistance compared to Ni or NiSiC coatings. It is also visible that the addition of detonation nanodiamond particles in the coating doesn't increase the surface roughness as SiC-particles do.

[0223] FIGS. 5a and 5b show wear tracks imaged with SEM for electrolytic nickel and Ni-ND 7.5 g/l. By looking at the width of the wear track and its appearance, it is clear that nanodiamond containing coating (FIG. 5b) has higher wear resistance.

[0224] The FIG. 5a features a wear track for a coating plated from pure electrolytic nickel, the FIG. 5b featuring a wear track manufactured from an electrolyte with 7.5 g/l of Hydrogen D contained detonation nanodiamonds.