RU2599473C1 - Method of electrochemical silver-nano-carbon-diamond coating producing - Google Patents

Abstract

FIELD: electroplating.

SUBSTANCE: invention relates to electroplating

and can be used in electronics, electrical engineering and other industries. Method includes electrochemical deposition from dicyanargentaterhodanate electrolyte, containing silver ions and modified detonation synthesis nano carbon diamond material, g/l: K[Ag(CN)₂] (calculated using Ag) - 20-35; K₂CO₃ - 40-50; KCNS - 150-200; modified by 5-30 % nitric acid nano-carbon-diamond material - 0.2-2.0, at temperature of 18-25 °C and current density of 0.5-2.0 A/dm².

EFFECT: technical result is reduction of specific resistance, coating porosity, its higher wear resistance and corrosion resistance with low consumption of diamonds and using simple process.

1 cl, 11 tbl, 1 ex

Description

This invention relates to the field of inorganic chemistry, namely to electrochemical (galvanic) silver coatings.

Silver-based electrochemical coating is widely used in electronic, radio engineering, electrical, jewelry and other industries.

State of the art

For the first time, composite electrochemical coatings (CEC) based on silver and detonation nanodiamonds (DNDs) were described in the copyright certificate [A.S. 1668490, USSR, C25D 3/46, 15/00, claimed 05/10/1989. Electrolyte for the deposition of silver coatings. N.B. Baltrunene, R.M. Vishomirskis, A.M. Molchadsky and A.I. Shebalin, BI No. 29, 1991. - P. 123, publ. 08/07/1991]. The aim of the work was to increase hardness while maintaining a high electrical conductivity of the coating. To achieve this goal, the authors used silver plating only from cyanide electrolyte of the following composition (g / l):

- potassium dicyanargentate (calculated on metal) - 15-60;

- potassium cyanide - 20-200;

- potassium carbonate - 5-20;

- standard detonation nanodiamonds - 0.03-0.8.

Comparative data for the known (prototype) electrolyte [M.A. Belenky, A.F. Ivanov. Electrodeposition of metal coatings. Directory. - M.: Metallurgy. - 1985. - 288 p.] And proposed by the authors A.S. 1668490 are given in table. one.

The electrodeposition process is carried out at a temperature of 18-25 ° C and a current density of 0.3-2 A / DM ² . Silver coatings have a microhardness of 240-480 kg / mm ² . The microhardness of the coatings was measured using a PMT-3 microhardness tester with a load of 200 g.

It is seen that the wear resistance of the coatings increased by ~ 2.5 times, the presence of pores in the coating (symbatically corrosion resistance) was not determined, the thickness of the silver coating is very large. Electrical resistivity is almost unchanged.

In the works of [V.Yu. Dolmatov, G.K. Burkat. Ultrafine detonation synthesis diamonds as the basis of a new class of composite metal-diamond electroplated coatings // Superhard materials. - 2000. - No. 1. - P. 84-95], the authors after testing various silver-containing electrolytes, chose a synerodisthanic silver electrolyte containing (g / l): silver salt - 25-30 (in terms of metal); potassium carbonate - 20-25, potassium thiocyanate - 80-120; red blood salt - 40-60, organic potassium salt - 15-20; standard detonation nanodiamonds (DND) - 0.2-2.0.

The wear resistance of silver-diamond coatings was determined by their abrasion by the method of reciprocating movements under load according to GOST 16875 - 71. The number of reciprocating movements per hour was 1500. The load per 1 cm ² of the 190 sample. The wear resistance of the samples was determined by the weight method for weight loss in% and to reduce the thickness in microns. The results are presented in table. 2.

According to the test results, it is seen that an increase in the concentration of DND increases the wear resistance of the coatings. Even with a thickness of 1.5-2 microns, it is possible to have a slightly wearable silver film, which will reduce in many cases the thickness of the silver coating and improve the quality of the products. Accordingly, to increase the service life of products coated with a layer of silver from the bottom. Electrical resistance (or electrical conductivity) was not determined.

The disadvantages of the method include insufficient wear resistance, lack of data on the porosity of the coating (corrosion resistance).

In the work [Application for a patent of the Russian Federation No. 96104061/02, C25D 3/46, 15/00 of 03/16/1995, the Method of coating based on silver, A.P. Korzhenevsky, T. M. Gubarevich, BI 1998 No. 12 (I), p. 67], the authors extended the scope of DND to various silvering electrolytes, including dicyanargentate, in order to reduce the toxicity and chemical aggressiveness of the electrolyte while maintaining high mechanical properties of CEC - hardness and wear resistance. The concentration ratio of the deposited metal and the dispersed phase was established from 50: 1 to 1: 1.

As a rule, the use of non-cyanic silver electrolytes leads to the production of coatings inferior in terms of the complex of electrophysical and mechanical characteristics to silver deposits from cyanide baths. The use of DND in the range claimed by the authors allows to obtain dense small-crystalline semi-shiny silver coatings containing 0.03-1.0% of the mass. diamond. These CECs have high microhardness and wear resistance, as well as enhanced technological properties.

DNDs introduced into the electrolyte are characterized by a negative charge on the surface of the particles and powerful adsorption ability. DND particles partially bind silver ions, which increases the cathodic polarization, promotes the formation of fine crystalline precipitates and avoids contact silver release.

The process of electrodeposition of composite silver-diamond coatings is carried out at an electrolyte temperature of 18-25 ° C at a constant (PT), pulsed (IT), reverse (RT) or combined electrolysis mode. The choice of a specific deposition mode depends on the requirements for the obtained CEC. So, to obtain a strong adhesion of the precipitate with the base, the process is started at an increased current density (3-5 A / dm ² ) from an electrolyte with a high relative content of DND. In this case, a dense layer with a high content of diamond particles is formed, which slows the mutual diffusion of the components of the base and coating. This increases the protective properties of the coatings and prevents the growth of transition resistance and passivation of precipitation. Then, electrodeposition is continued at a current density of 0.1-3 A / dm ² (depending on the composition of the electrolyte), as a result, a layer of plastic, smooth, wear-resistant silver with electrophysical characteristics close to pure metal is obtained.

A positive effect, expressed in obtaining silver-diamond CEC with improved mechanical characteristics, is achieved when the concentration ratio of silver and DND in the electrolyte is from 50: 1 to 1: 1. In this concentration range, the equilibrium of adsorption-bound and soluble silver complexes is realized, which is favorable for the coprecipitation of metal and particles of the dispersed phase. A decrease in the relative concentration of DND below the ratio Ag: DND = 50: 1 (0.4-0.6 g / L DND) leads to a decrease in cathodic polarization and the formation of coarse-grained precipitates, which have low hardness and wear resistance and unstable electrophysical properties. An increase in the relative concentration of DND by more than 1: 1 (20-30 g / l DND) to the deposited metal leads to the inclusion of loose aggregated particles in the coating, a violation of the uniformity of the precipitate and the deterioration of its mechanical and electrophysical characteristics. In addition, there is a decrease in the value of the limiting current, which affects the manufacturability of the method.

The introduction of nanodispersed diamonds into non-cyanide silver electrolytes in the indicated ratio with the deposited metal results in highly hard precipitates. Depending on the electrolysis mode, composition and type of non-cyanide electrolyte, the microhardness of CEC increases by 200-700 MPa (~ 20-70 kg / mm ² ) in comparison with pure silver deposited under the same conditions. Wear resistance of coatings increases by 1.3-2.6 times. However, the electrical resistivity increases from 1.65 · 10 ^-6 to 1.75 · 10 ^-6 Ohm · cm.

With an increase in the diamond content in the sediment (from 0.1 to 1%), an increase in the hardness and wear resistance of the CEC is observed.

Grinding of sediment grain during electrodeposition from an electrolyte suspension occurs due to the introduction of particles into the matrix, as well as a result of the mechanical action of these particles on the matrix surface during the deposition process. The introduction of DND into the silvering electrolyte in the ratio (1: 1) - (1:50) to the deposited metal leads to a decrease in the grain size of the precipitate by 20-65% depending on the electrolysis mode, and this effect is most significant at high current densities.

Moving colloidal diamond particles have a depassivating effect on the anode processes, which makes it possible to intensify the deposition process by using higher current densities. During the deposition of coatings from a DND-containing electrolyte, a smoothing effect of diamond particles is observed, which prevents the formation of dendrites, which are obtained, as a rule, during silvering from a pure electrolyte.

The application of the Ag-DND CEC can be carried out at a constant current within the parameters recommended usually to obtain functional silver coatings from one or another electrolyte.

In the table. Figure 3 shows the deposition of a silver coating with standard (unmodified) DNDs. To do this, in a silver cyanogenate electrolyte having the composition (g / l): K [Ag (CN) ₂ ] (per metal) - 20, KCNS - 150, K ₂ СО3 - 30, pH = 10.1, the calculated amount of DND is introduced in the form of an aqueous colloid so that the ratio of the Ag: DN concentration is 60: 1, 50: 1, 25: 1, 1: 1, 0.5: 1. The deposition of the CEC is carried out at 20 ° C, constant stirring of the electrolyte. The cathodic density of direct current is 2 A / DM ² . The results of studies of the properties of the obtained CEC are given in table 3.

From table 3 it is seen that the maximum microhardness of ~ 1450 MPa (~ 145 kg / mm ² ) was achieved, the wear resistance is 2 times higher than that of coatings without DND with an increase in resistivity.

The disadvantages of the method are:

1) low wear resistance (only 1.5-2.0 times higher);

2) a large number of used DNDs (up to 20-30 g / l);

3) a decrease in the domains (grains) of silver deposit only by 20–65% (1.2–1.65 times);

4) increase in the specific resistance of the coating (from 1.65 × 10 ^-6 to 1.75 × 10 ^-6 Ohm · cm), that can prevent the use of such coatings in electronics and electrical engineering.

The prototype of the present invention is the method described in the work of [RF Patent No. 2404294 of 11.29.2007. Composite metal-diamond coating, method for producing it, electrolyte, diamond-containing electrolyte additive and method for its preparation. G.K. Burkat, V.Yu. Dolmatov, E.A. Orlova, publ. 11/20/2010].

To obtain a silver coating using a modified diamond-containing mixture of detonation synthesis (MASH), obtained according to [RF Patent No. 2046094 from 05/26/1993. Synthetic carbon diamond material. T.M. Gubarevich, V.Yu. Dolmatov, V.A. Marchukov]. This material consists of, by weight. %: carbon 60-85; hydrogen 0.6-3.3; nitrogen 1.4-3.4; oxygen 13.3-33.0; while carbon consists of 60-92 wt. % detonation nanodiamonds and 8-40 wt. % non-diamond forms of carbon. This material is obtained by processing the initial detonation diamond-containing charge (AS) with 57% nitric acid (2-5 hours) by heating to a decrease in the mass of the initial charge, comprising 5-50 wt. %

A typical example: 10 g of the original AS is placed in 500 ml of 57% nitric acid, heated to boiling, the processing time is 4 hours, the mass loss of AS is 23%. The resulting MASH consists of 77.4 wt. % DND and 22.6 wt. % non-diamond carbon.

This MASH is introduced, according to the prototype, into a silver cyanogenate electrolyte composition, g / l:

KAg (CN) ₂ - 24 (calculated on metal);

K ₂ CO ₃ - 40;

KCNS - 80;

MASH - 0.1-10.0;

i _k = 0.7 A / dm ² ;

t = 20 ° C.

Compared to silver-diamond coatings obtained from a similar silver electrolyte containing DND particles, the resulting coating has a higher microhardness - 1.2-1.4 times higher (without additives, the microhardness of the silver coating is 80 kg / mm ² , with DND - max 140 kg / mm ² , with MASH - max 182 kg / mm ² ) and higher wear resistance - 2.5-4.0 times higher (without additives, wear resistance is taken as 1, with DND - max 2.0, s MASH - max 6.1).

When the initial AS is treated with 57% nitric acid during boiling for 2-5 hours, not only the easily oxidized and disordered non-diamond, but also graphite-like carbon is removed, and the composition of the MAC is close to the purified DND. All this leads to the absence of MAS in the deposited particles in the silver coating of conductive graphite particles and to an obvious increase in electrical resistivity.

Disclosure of invention

The basis of this invention is the task of creating such a method for producing silver-nanocarbon-diamond coating (SNUAP), which would make it possible to obtain coatings with low resistivity, increased wear resistance, low porosity and, accordingly, increased corrosion resistance at a low consumption of cheap modified nanocarbon-diamond material and simple technology, which will significantly increase the resource of products with such a coating and expand the range of their application.

This problem is solved by the fact that the proposed method for producing SNAP, including electrochemical deposition from dicyanogenate-hydrogen-containing electrolyte containing silver ions and nanocarbon-diamond material of detonation synthesis, modified with 5-30% nitric acid, composition (g / l):

Ag (calculated on the metal) - 20-35;

K ₂ CO ₃ - 40-50;

KCNS - 150 ÷ 200;

Modified nanocarbon-diamond material (MNUAM) - 0.2-2.0;

at a temperature of 18-25 ° C and a cathodic current density of 0.5-2.0 A / dm ² .

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in detail and is not limited to the foregoing claims.

MNUAM do not represent an individual chemical compound or a homogeneous physical structure, they have a complex structure.

In the process of detonation in the preparation of AS, the decay of explosive molecules provides a high concentration of free carbon, more precisely, a radical-like C ₂ dimer in a limited time and volume "zone of chemical reactions" behind the front of the detonation wave. There is a qualitative incompatibility of strongly nonequilibrium conditions in the “zone of chemical reactions” with the formation of a stable crystalline phase of diamond. Therefore, the process of DND formation (due to the very short time of existence (<0.3 · 10 ^-6 s) of the necessary pressure, temperature, and concentration (in terms of carbon) conditions) does not follow the crystallization of nanoscale diamond, but in the process of carbon self-organization into the condensed phase compliance with the basic chemical properties of carbon through the formation of a diamond-like nucleus (adamantane), followed by growth by the diffusion mechanism due to the attack of the nucleus by C ₂ dimers [Dolmatov V.Yu., V. Mullyumaki, A. Vehanen. A possible mechanism for the formation of nanodiamonds during detonation synthesis // Superhard materials. - 2013. - No. 3. - S. 19-28]. A fractal carbon network is likely to occur with simultaneous fluctuations in carbon density. At the “nodes” of this grid with the highest density (most likely, adamantane) a three-dimensional ordered nucleus (DND) is formed, and regions with a lower carbon density are repeatedly destroyed and recombined during the expansion of detonation products.

T.O. having undergone the whole complex of thermal shock and chemical attacks from detonation gas products (СО, СО ₂ , Н ₂ O, HCN, N _x O _y , Н ₂ , СН ₄ , etc.), AS becomes a substance of the most complex structural organization , including pronounced crystalline (nanodiamond) particles, continuously transforming into more loose and less ordered spatial carbon formations with a wide spectrum of energy states and the type of interatomic and intermolecular bonds.

A feature of AS should be considered its state: on the one hand, this material underwent a kind of “hardening” in harsh detonation conditions, and on the other hand, it is the most chemically active (in our case, excessively active) of the known forms of carbon. This duality of the AS is the basis of its practically significant properties, including the possibility of using AS (after appropriate modifications) in galvanic processes, in particular in silvering processes.

The composition of AS includes 40-50 wt. % DND and 50-60 wt. % non-diamond carbon, mainly nanographite. The aim of treating AS with weak (5-30%) nitric acid is to remove (oxidize) disordered carbon and preserve nanographite with the formation of MNUAM. It is empirically established that nanographite is preserved by boiling in acid with a concentration of the above range up to 1.5 hours.

After cooling the suspension of MNUAM and its 3-4 water washes, a very stable colloidal stable aqueous suspension of MNUAM is obtained (MNUAM does not precipitate for 6 months), which greatly expands the range of its use in all possible processes.

During the electrodeposition of silver, MNUAM particles are introduced into the precipitate and have a significant effect on the structure and properties of the latter. The hardening process occurs due to interference caused by particles, dislocation movement in the plane of their slip. It is also known that pores and particles in a material inhibit grain growth. With a decrease in particle size and constant volume concentration, the distance between the particles decreases, which leads to the formation of thin metal films, which are more durable than a compact material. But most importantly, the presence of nanographite in the coating, in addition to DND, significantly increases the electrical conductivity of the silver coating.

Particles of MNUAM nanographite, due to their small size and surface chemical activity, included in silver sediment, improve its electrophysical properties in contrast to silver-corundum CEC. The small size of MNUAM particles contributes to their uniform distribution and dispersion in the volume of the metal matrix, because the motion of such particles in a liquid is Brownian.

Non-cyanide electrolytes containing MNUAM in the indicated ratio with silver exhibit high stability due to the small size of diamond and nanographite particles, their chemical resistance, and hydrophilic surface properties of DND and nanographite. The introduction of MNUAM into the electrolyte is carried out by adding the calculated amount of material previously suspended in water. The electrolyte is mixed by pumping, mechanical or acoustic mixing.

MNUAM was introduced into the silver electrolyte in the form of an aqueous suspension. The electrolysis temperature was maintained in the range of 18-25 ° C, the cathodic current density from 0.5 to 2.0 A / DM ² .

It was experimentally established that when using MNUAM, the optimal concentration of silver per metal is 20-35 g / l.

The microhardness of the coatings was compared using a PMT-5 microhardness tester. The wear resistance of the coatings was investigated using an abrasion apparatus. The porosity of the coatings was estimated by the method of taking anode polarization curves. The structure of the coatings was studied using a JCM - 35 CF scanning electron microscope. The coating composition was studied using an AN 7529M rapid carbon analyzer (automatic titration method by pH value). The electrical conductivity of the precipitation was measured using an E6-18 / 1 milliometer.

With an increase in the concentration of potassium thiocyanate from 0 to 150 g / l, the cathode curves and current-free potential shift to the electronegative side. This is explained by the fact that if in silver cyanide electrolytes without free cyanide content the potential is much higher than in electrolytes with free cyanide content due to incomplete ion complexation, then in cyanide electrolyte, the role of free cyanide is played by rhodanide, and the current-free potential shifts to the electronegative region. Such an electrolyte has mixed complexes, and ions of the type [Ag (CN) ₂ (CNS) ₂ ] ^- or [Ag (CN) (CNS) ₂ ] ^2- contained in the electrolyte participate in the cathodic process.

The product of the anodic reaction is tetrarodanoargent [Ag (CNS) 4] ^3- . Accordingly, with an increase in the concentration of potassium thiocyanate, the dissolution process should be facilitated. What is confirmed by anode curves. Without potassium thiocyanate, the passivation current is at least 0.3 A / dm ² . With the addition of potassium thiocyanate 75 g / l, the passivation current increases by a factor of 2, which indicates that the dissolution of silver proceeds with the formation of a thiocyanate complex. With a further increase in potassium thiocyanate, the passivation current increases almost proportionally.

With an increase in the concentration of potassium thiocyanate, the exchange current increases. This is due to the fact that the anode process is significantly accelerated (5 times with an increase in concentration to 200 g / l KCNS). The acceleration of the reaction is also explained by the fact that with an increase in the concentration of potassium thiocyanate, the thiocyanate complex prevails in the anode reaction, and in the cathode region the discharge comes from mixed and cyanide complexes.

An increase in the concentration of KCNS in the electrolyte increases the conductivity, which can be explained by an increase in the alkalinity of the electrolyte as a result of hydrolysis of KCNS, as a salt of a weak acid.

When MNUAM is introduced into the electrolyte (Table 4), the electrical conductivity increases almost 2 times, this can be explained by the high electrical conductivity of nanographite particles in solution.

The dissipating ability of the electrolyte characterizes the uniformity of the coating, if it is low, the electroplating process is complicated, additional anodes and devices are required to cover the part of complex shape. Based on the study of the polarization and electrical conductivity of solutions with and without additives, electrochemical similarity coefficients characterizing the dissipative ability of electrolytes were calculated.

The scattering ability of the electrolyte with the addition of MNUAM increases by 2.0 times (table. 5). This is due to the fact that the introduction of MNUAM changes the polarizability and electrical conductivity of the electrolyte, because this additive behaves as a mild surfactant (surfactant).

It was found that the silver coating sample obtained without MNUAM has a pronounced coarse-crystalline structure in comparison with samples obtained in the presence of MNUAM. They have a uniform dense structure. MNUAM strongly crush the structure of coatings, as shown in the table. 6, where the grain size in the presence of additives decreases almost 3 times and the density of silver increases significantly. In particular, this can be explained by the surface-active properties of MNUAM in this electrolyte and their action as a composite additive.

The microhardness of the silver coating in the presence of MNUAM increased from 80 kg / mm ² (without additives) to 118 kg / mm ² (Table 7).

Silver is a precious metal, and often its thickness is 3 microns or less. It is necessary that even with minimal thicknesses the coating does not wear out for a long time. Therefore, a very important property for silver is wear resistance. The experimental data obtained during the research are summarized in table. 8. For comparison, wear resistance was determined on silver coatings (without additives) obtained at a current density of 0.5 A / dm ² . At a concentration of MNUAM of 1.5 g / l, the wear resistance of the coating increases by 3–6 times (Table 8).

An important physicochemical property is the porosity of the resulting coating. The porosity study was carried out by the method of taking anodic polarization curves in a solution of 1 N. H ₂ SO ₄ , to assess the porosity, a potential of 250 mV was chosen, in which the silver coating remains in a passive state, and the copper base dissolves at a sufficiently high speed.

To select the potential at which the current – time curves were taken, the anodic polarization curves for silver and copper in a 1 N solution were taken. H ₂ SO ₄ .

The calculation data presented in table. 9 show that when MNUAM is introduced into a silver electrolyte, the porosity of the coatings decreases even at a thickness of 3 μm. MNUAM reduces porosity even more at a concentration of 0.5 g / l and a current density of 0.3 A / dm ² , almost 5 times (table. 9).

To confirm that MNUAM are included in the coatings and affect the structure, an analysis was carried out on the carbon content in the coating. The results are summarized in table. 10.

From the table. 10 shows that the content of MNUAM in the coating depends on their concentration in the electrolyte.

From table 11 it is seen that as the amount of MNUAM in the silvering electrolyte increases and as the current density increases, the electrical resistivity drops 1.4–2.9 times, which significantly increases the electrical conductivity of the silver-nanocarbon-diamond coating.

When the Ag content (calculated per metal) in the dicyanargentate electrolyte with MNUAM is less than 20 g / l, the silver coating is highly porous (at 18 g / l Ag, current density 1.5 A / dm ^2, the pore area reaches 1.92%). When the Ag content is more than 35 g / l, the wear resistance increases only 2 times (at 37 g / l Ag and a current density of 1.5 A / dm ² ).

The content of K ₂ CO ₃ in 40-50 g / l is typical for cyanogenate electrolyte and is not subject to discussion. The need for KCNS content in the range of 150-200 g / l is discussed in detail previously.

The discovered positive effect of the use of the MNUAM additive in the cyanogenate electrolyte is as follows:

- increase the electrical conductivity of coatings by 1.5-3.0 times;

- increase the wear resistance of the silver coating by 3-6 times;

- decrease in coating porosity (symbatic increase in corrosion resistance) by 5 times;

- an increase in the scattering ability (uniformity of coating over the thickness) by 2 times;

- a reduction in the coating grain by a factor of 3 is achieved when the concentration of MNUAM in the electrolyte is from 0.2 to 2.0 g / l;

- increase the microhardness of the coating up to 1.5 times.

The essence of the method is illustrated by examples of its implementation, but is not limited to them.

Example No. 1

A) Obtaining MNUAM

0.5 l of 20% nitric acid is poured into a heat-resistant glass with a capacity of 1 l and 50 g of AS are poured, the suspension is brought to boiling with stirring and kept for 1 h at boiling, after which the suspension is poured into 4 l of distilled water located in 5- liter capacity, mix thoroughly and leave for 1 day. After the specified period has elapsed, clarified water is decanted (on top of the suspension) and fresh water is poured, the process is repeated until a pH of ~ 6 is reached. Next, from a concentrated precipitate containing MNUAM, a sample is taken for analysis, the concentration of MNUAM is determined and adjusted to 5 wt. % Similarly treated with HUAM 5% and 30% nitric acid.

B) Obtaining coverage

In a heat-resistant glass with a capacity of 150 ml, 100 ml of distilled water is poured, 9.5 g of potassium dicyanargentate are dissolved in it (when heated to 30 ° C). In a separate heat-resistant glass with a capacity of 100 ml, 50 ml of distilled water is poured and 30 g of rhodanic potassium is dissolved, heating the solution to 30-50 ° C. In a third heat-resistant glass with a capacity of 100 ml, 50 ml of distilled water is poured, 8 g of potassium carbonate is dissolved in it, heating the solution to 30-50 ° C. All dissolved components are mixed in a separate glass with a capacity of 200 ml. After the preparation of the dicyanoargent native silver electrolyte, 2 g of an aqueous 5% solution of MNUAM (0.5 g / l) are introduced into it.

Before the experiment, the solution is required to bring the solution to an operating temperature of 18-25 ° C. To do this, the prepared electrolyte is poured into a heat-resistant glass and heated to a laboratory tile. After that, the silvering electrolyte is poured into a 250 ml polypropylene bath. Anodes (plates of the Cp brand 99.99%) are immersed in silver plating electrolyte so that they are located at an equidistant distance from the coated part. To prevent settling of coagulated particles, an anchor for an electromagnetic mixer is placed in the electrolyte solution. The magnetic stirrer turns on. The part is immersed in electrolyte. The positive pole of the current source is connected to the anodes, and the negative pole to the part. The current is set based on a current density of 0.4-0.6 A / dm ² . The source should provide the ability to set the current with an accuracy of 0.01 A. Turn on the current source.

After the process, the current source is turned off, the part is taken out, thoroughly washed and dried.

Preparation process

The technological process for the preparation of parts from copper and steel (carbon and low alloy) alloys consists of the following steps:

- removal of oxides and mechanical grinding - washing in cold running water;

- chemical degreasing;

- washing in warm water;

- washing in cold water;

- activation in a solution of the composition: sulfuric acid - 50 g / l;

- washing in cold water;

- silvering.

The specific electrical resistance of the obtained silver coating is 8.6 · 10 ^-3 Ohm · mm ² / m, for a pure silver coating - 23.1 · 10 ^-3 Ohm · mm ² / m (decreases 2.9 times).

The wear of the resulting silver coating is 14% of the weight of the coating, under the same conditions of obtaining the wear of a pure silver coating is 57%.

The endurance test is carried out on the installation, providing reciprocating motion of the sample. The rubbing pair is a brass disk with a diameter of ~ 15 mm with a galvanic coating applied to it. The disk moves along a fixed plane-parallel steel plate coated with hard chrome. As a load on the sample, a removable weight of 130 g is used. The wear resistance of the coating is determined by the loss of mass of the sample during the test, which is 20 hours.

The porosity of the resulting silver coating is 0.83% (pore area), while the pure silver coating is 3.47%.

The carbon content in the resulting silver coating is 0.11 wt. %, in a pure silver coating - 0.01 wt. %

Other examples of the process are described in tables 4-11.

Industrial applicability

The developed method can be used in the electrochemical and electronic industries.

Claims (1)

A method of obtaining an electrochemical silver-nanocarbon-diamond coating, including the deposition of dicyanogenate-hydrogen-containing electrolyte containing silver ions and nanocarbon-diamond material of detonation synthesis in the form of an aqueous suspension at a temperature of 18-25 ° C and a current density of 0.5-2.0 A / dm ² , characterized in that the use of nanocarbon-diamond material modified with 5-30% nitric acid in the electrolyte composition, g / l:
K [Ag (CN) ₂ ] (based on Ag) 20-35 K ₂ CO ₃ 40-50 Kcns 150-200 modified nanocarbon-diamond material 0.2-2.0