阅读说明：本技术 一种石墨烯-烟酸镀银液及制备方法 (Graphene-nicotinic acid silver plating solution and preparation method thereof ) 是由 周铭 李虓 陈鑫 罗超贵 全金 于 2021-06-16 设计创作，主要内容包括：本发明涉及一种石墨烯-烟酸镀银液及制备方法。所述的石墨烯-烟酸镀银液,由包括以下重量份的原料制成：银盐30-50、配位剂80-100、缓冲液60-70、导电盐60-70、添加剂30-50、石墨烯0.3-0.5、水700-1100。本发明的石墨烯-烟酸镀银液组成合理,成分稳定、能够使石墨烯均匀分散,具有良好的推广应用价值。(The invention relates to a graphene-nicotinic acid silver plating solution and a preparation method thereof. The graphene-nicotinic acid silver plating solution is prepared from the following raw materials in parts by weight: 30-50 parts of silver salt, 80-100 parts of complexing agent, 60-70 parts of buffer solution, 60-70 parts of conductive salt, 30-50 parts of additive, 0.3-0.5 part of graphene and 700 parts of water. The graphene-nicotinic acid silver plating solution disclosed by the invention is reasonable in composition and stable in components, can uniformly disperse graphene, and has good popularization and application values.)

1. The graphene-nicotinic acid silver plating solution is characterized by being prepared from the following raw materials in parts by weight: 30-50 parts of silver salt, 80-100 parts of complexing agent, 60-70 parts of buffer solution, 60-70 parts of conductive salt, 30-50 parts of additive, 0.3-0.5 part of graphene and 700 parts of water.

2. The graphene-nicotinic acid silver plating solution according to claim 1, wherein the preparation method comprises the following steps:

s1, dissolving silver salt, a complexing agent, a buffer solution, conductive salt and an additive into water to obtain electroplating solution;

s2, adding ammonia water into the electroplating solution to adjust the pH value to 9.5-10.5 to obtain a silver plating solution a;

s3, adding graphene powder particles into 30-50% of the total amount of the silver plating solution a, uniformly stirring, adding a dispersing agent, performing ultrasonic treatment for 15-30min, adding the rest silver plating solution a, uniformly stirring, and performing ultrasonic treatment for 15-30min again to obtain the silver plating solution.

3. The graphene-nicotinic acid silver plating solution of claim 1 or 2, wherein: the silver salt is silver nitrate.

4. The graphene-nicotinic acid silver plating solution of claim 1 or 2, wherein: the complexing agent is nicotinic acid.

5. The graphene-nicotinic acid silver plating solution of claim 1 or 2, wherein: the buffer solution is ammonium acetate buffer solution, and the concentration of the buffer solution is 60g/L-70 g/L.

6. The graphene-nicotinic acid silver plating solution of claim 1 or 2, wherein: the conductive salt is potassium carbonate.

7. The graphene-nicotinic acid silver plating solution of claim 1 or 2, wherein: the additive is potassium hydroxide.

8. The graphene-nicotinic acid silver plating solution of claim 2, wherein:

the environment-friendly coating also comprises a dispersant, wherein the dispersant is sodium dodecyl sulfate, sodium dodecyl sulfate and polyethylene glycol-400;

wherein the weight ratio of the sodium dodecyl sulfate to the sodium dodecyl sulfate is 1-2:1-2, the total weight of the sodium dodecyl sulfate and the sodium dodecyl sulfate is 5-20% of the weight of the added graphene powder, and the addition amount of the polyethylene glycol-400 is 0.5-1% of the weight of the silver plating solution a.

9. The graphene-nicotinic acid silver plating solution of claim 1, wherein: saidThe electroplating using conditions of the silver plating solution a are as follows: the current density of electroplating is 0.2-0.3A/dm²The electroplating time is 30-50min, and the temperature is 25-30 ℃.

Technical Field

The invention relates to the technical field of electrochemical composite electrodeposition, in particular to graphene-nicotinic acid silver plating solution and a preparation method thereof.

Background

In the prior art, the most widely studied and applied silver-based electric contact materials are the electric contact materials, but high-purity silver metal has the defects of poor adhesion and electric wear resistance, low melting point, low hardness and the like. Silver metal is easy to form a silver sulfide film on the surface in a medium containing sulfur or sulfide. Under the action of direct current, silver metal is easy to volatilize and form electric erosion spikes, so that the silver contact element is easy to form electric arcs and is welded.

Especially under the working conditions of large and medium power contacts, the pure silver-based electric contact material cannot meet the requirements because of severe electric erosion under the strong action of electric arcs.

The graphene with excellent electrical, thermal, mechanical and other properties can be used as a reinforcement to be applied to a metal matrix composite material so as to improve the properties of the metal material and adapt to the application of modern industry. The main method for introducing graphene at present is a composite electrodeposition technology. The electrodeposition method mainly adopts a composite electroplating process, pure silver is used as an anode, a substrate metal is used as a cathode, and a composite plating layer is obtained by transferring and depositing ions and graphene particles in a silver salt solution. Investigation and statistics show that nearly 90% of the current domestic silver electroplating production lines all adopt a cyanide complex system, but the cyanide silver plating solution is extremely toxic. As early as 2005, the national development and improvement commission 40 document has positioned cyanidation electroplating as an obsolete, out-dated production process.

The biggest technical difficulty in introducing graphene after cyaniding electroplating is stopped is that graphene is easy to agglomerate in silver plating solution and is not uniformly dispersed when being compounded on a silver plating layer. Therefore, the cyanide-free silver plating solution with stable components and capable of uniformly dispersing graphene is urgently needed to be found in the field.

Disclosure of Invention

The graphene-nicotinic acid silver plating solution has reasonable composition and stable components, can uniformly disperse graphene, and has good popularization and application values.

The purpose of the invention is realized by the following technical scheme:

the graphene-nicotinic acid silver plating solution is prepared from the following raw materials in parts by weight: 30-50 parts of silver salt, 80-100 parts of complexing agent, 60-70 parts of buffer solution, 60-70 parts of conductive salt, 30-50 parts of additive, 0.3-0.5 part of graphene and 700 parts of water.

The preparation method of the graphene-nicotinic acid silver plating solution comprises the following steps:

s1, dissolving silver salt, a complexing agent, a buffer solution, conductive salt and an additive into water to obtain electroplating solution;

s2, adding ammonia water into the electroplating solution to adjust the pH value to 9.5-10.5 to obtain a silver plating solution a;

s3, adding graphene powder particles into 30-50% of the total amount of the silver plating solution a, uniformly stirring, adding a dispersing agent, performing ultrasonic treatment for 15-30min, adding the rest silver plating solution a, uniformly stirring, and performing ultrasonic treatment for 15-30min again to obtain the silver plating solution.

The silver salt is silver nitrate.

The complexing agent is nicotinic acid.

The buffer solution is ammonium acetate buffer solution, and the concentration of the buffer solution is 60g/L-70 g/L.

The conductive salt is potassium carbonate.

The additive is potassium hydroxide.

The graphene-nicotinic acid silver plating solution also comprises a dispersing agent, wherein the dispersing agent is sodium dodecyl sulfate, sodium dodecyl sulfate and polyethylene glycol-400;

wherein the weight ratio of the sodium dodecyl sulfate to the sodium dodecyl sulfate is 1-2:1-2, the total weight of the sodium dodecyl sulfate and the sodium dodecyl sulfate is 5-20% of the weight of the added graphene powder, and the addition amount of the polyethylene glycol-400 is 0.5-1% of the weight of the silver plating solution a.

The electroplating using conditions of the silver plating solution a are as follows: the current density of electroplating is 0.2-0.3A/dm²The electroplating time is 30-50min, and the temperature is 25-30 ℃.

According to the invention, a preliminary buffer balance system is formed by using the coordination agent and the buffer solution, and then the dispersing agent with a unique composition is matched, so that the uniform and consistent dispersion of graphene is realized, and the dispersion system has stable property and can fully meet the requirements of an electroplating process. Compared with the prior art, the silver plating layer electroplated by the silver plating solution has better wear resistance and ablation resistance, and has good popularization and application values.

The preparation method of the silver plating solution provided by the invention can make the graphene-nicotinic acid silver plating solution more stable and uniform and better ensure the stability of subsequent electroplating.

The invention also provides the electroplating condition of the silver plating solution in the preferred scheme, and the electroplating condition can better exert the performance of the silver plating solution.

Drawings

FIG. 1 is a contact angle of a plating solution containing graphene under different dispersant systems;

FIG. 2 shows Zeta potential of a plating solution containing graphene plating solution in the same dispersant system;

FIG. 3 shows the morphology of the plating layer prepared by the pure silver plating solution and the silver-graphene plating solution;

FIG. 4 is a Raman spectrum of graphene on the surface of the bump structure in the plating layer shown in FIG. 3 (b);

FIG. 5 is an EDS spectrum of the plated layer after polishing;

fig. 6 is a surface view of the pure silver plating and the silver-graphene plating after 72 hours;

FIG. 7 is a Raman spectrum of graphene on the surface of a coating of a graphene silver plating system of nicotinic acid and succinimide;

FIG. 8 is a topographical map of surface wear scars on groups after dry rubbing;

FIG. 9 is a diagram showing the shape of a contact after 10000 times of on/off operations of each group.

Detailed Description

The invention is further illustrated by the following examples. It should be understood that the examples of the present invention are for illustrative purposes and not intended to limit the present invention. Simple modifications of the invention in accordance with its spirit fall within the scope of the claimed invention.

Example 1

The graphene-nicotinic acid silver plating solution comprises the following components: 30g of silver nitrate, 80g of nicotinic acid, 60g of 60g/L ammonium acetate buffer solution, 60g of potassium carbonate, 30g of potassium hydroxide, 0.3g of graphene and 700g of water;

the environment-friendly coating also comprises a dispersant, wherein the dispersant is sodium dodecyl sulfate, sodium dodecyl sulfate and polyethylene glycol-400;

wherein the weight ratio of the sodium dodecyl sulfate to the sodium dodecyl sulfate is 1:1, the total weight of the sodium dodecyl sulfate and the sodium dodecyl sulfate is 5 percent of the weight of the added graphene powder, and the adding amount of the polyethylene glycol-400 is 0.5 percent of the weight of the silver plating solution a.

The preparation method of the graphene-nicotinic acid silver plating solution comprises the following steps:

s1, dissolving silver salt, a complexing agent, a buffer solution, conductive salt and an additive into water to obtain electroplating solution;

s2, adding ammonia water into the electroplating solution to adjust the pH value to 9.5, and obtaining a silver plating solution a;

s3, adding graphene powder particles into 30% of the silver plating solution a, stirring uniformly, adding a dispersing agent, carrying out ultrasonic treatment for 15min, adding the rest silver plating solution a, stirring uniformly, and carrying out ultrasonic treatment for 15min again to obtain the silver plating solution.

The electroplating using conditions of the silver plating solution a are as follows: the current density of the electroplating is 0.2A/dm²The plating time is 30min, and the temperature is 25 ℃.

Example 2

The graphene-nicotinic acid silver plating solution comprises the following components: 50g of silver nitrate, 100g of nicotinic acid, 70g of ammonium acetate buffer solution with the concentration of 70g/L, 70g of potassium carbonate, 50g of potassium hydroxide, 0.5g of graphene and 1100g of water;

the environment-friendly coating also comprises a dispersant, wherein the dispersant is sodium dodecyl sulfate, sodium dodecyl sulfate and polyethylene glycol-400;

wherein the weight ratio of the sodium dodecyl sulfate to the sodium dodecyl sulfate is 1:2, the total weight of the sodium dodecyl sulfate and the sodium dodecyl sulfate is equal to 20% of the weight of the added graphene powder, and the addition amount of the polyethylene glycol-400 is equal to 1% of the weight of the silver plating solution a.

The preparation method of the graphene-nicotinic acid silver plating solution comprises the following steps:

s1, dissolving silver salt, a complexing agent, a buffer solution, conductive salt and an additive into water to obtain electroplating solution;

s2, adding ammonia water into the electroplating solution to adjust the pH value to 10.5, and obtaining a silver plating solution a;

s3, adding graphene powder particles into 50% of the silver plating solution a, uniformly stirring, adding a dispersing agent, performing ultrasonic treatment for 30min, adding the rest silver plating solution a, uniformly stirring, and performing ultrasonic treatment for 30min again to obtain the silver plating solution.

The electroplating using conditions of the silver plating solution a are as follows: the current density of the electroplating is 0.3A/dm²The electroplating time is 50min, and the temperature is 30 ℃.

Example 3

The graphene-nicotinic acid silver plating solution comprises the following components: 40g of silver nitrate, 90g of nicotinic acid, 65g of ammonium acetate buffer solution with the concentration of 65g/L, 65g of potassium carbonate, 40g of potassium hydroxide, 0.4g of graphene and 900g of water;

the environment-friendly coating also comprises a dispersant, wherein the dispersant is sodium dodecyl sulfate, sodium dodecyl sulfate and polyethylene glycol-400;

wherein the weight ratio of the sodium dodecyl sulfate to the sodium dodecyl sulfate is 1.5:1, the total weight of the sodium dodecyl sulfate and the sodium dodecyl sulfate is equal to 15% of the weight of the added graphene powder, and the addition amount of the polyethylene glycol-400 is equal to 0.7% of the weight of the silver plating solution a.

The preparation method of the graphene-nicotinic acid silver plating solution comprises the following steps:

s1, dissolving silver salt, a complexing agent, a buffer solution, conductive salt and an additive into water to obtain electroplating solution;

s2, adding ammonia water into the electroplating solution to adjust the pH value to 10 to obtain a silver plating solution a;

s3, adding graphene powder particles into 40% of the silver plating solution a, stirring uniformly, adding a dispersing agent, carrying out ultrasonic treatment for 15-30min, adding the rest silver plating solution a, stirring uniformly, and carrying out ultrasonic treatment for 20min again to obtain the silver plating solution.

The electroplating using conditions of the silver plating solution a are as follows: the current density of the electroplating is 0.25A/dm²The plating time is 40min, and the temperature is 27 ℃.

Example 4

The graphene-nicotinic acid silver plating solution comprises the following components: 45g of silver nitrate, 85g of nicotinic acid, 67g/L of concentration, 63g of ammonium acetate buffer solution, 67g of potassium carbonate, 45g of potassium hydroxide, 0.5g of graphene and 800g of water;

the environment-friendly coating also comprises a dispersant, wherein the dispersant is sodium dodecyl sulfate, sodium dodecyl sulfate and polyethylene glycol-400;

wherein the weight ratio of the sodium dodecyl sulfate to the sodium dodecyl sulfate is 2:1, the total weight of the sodium dodecyl sulfate and the sodium dodecyl sulfate is 13 percent of the weight of the added graphene powder, and the adding amount of the polyethylene glycol-400 is 0.6 percent of the weight of the silver plating solution a.

The preparation method of the graphene-nicotinic acid silver plating solution comprises the following steps:

s1, dissolving silver salt, a complexing agent, a buffer solution, conductive salt and an additive into water to obtain electroplating solution;

s2, adding ammonia water into the electroplating solution to adjust the pH value to 9.7, and obtaining a silver plating solution a;

s3, adding graphene powder particles into 35% of the silver plating solution a, stirring uniformly, adding a dispersing agent, carrying out ultrasonic treatment for 18min, adding the rest silver plating solution a, stirring uniformly, and carrying out ultrasonic treatment for 16min again to obtain the silver plating solution.

The electroplating using conditions of the silver plating solution a are as follows: the current density of the electroplating is 0.23A/dm²The plating time was 37min and the temperature was 26 ℃.

Example 5

The graphene-nicotinic acid silver plating solution comprises the following components: 35g of silver nitrate, 95g of nicotinic acid, 66g of ammonium acetate buffer solution with the concentration of 62g/L, 63g of potassium carbonate, 35g of potassium hydroxide, 0.3g of graphene and 1000g of water;

the environment-friendly coating also comprises a dispersant, wherein the dispersant is sodium dodecyl sulfate, sodium dodecyl sulfate and polyethylene glycol-400;

wherein the weight ratio of the sodium dodecyl sulfate to the sodium dodecyl sulfate is 2:1.5, the total weight of the sodium dodecyl sulfate and the sodium dodecyl sulfate is equal to 17% of the weight of the added graphene powder, and the addition amount of the polyethylene glycol-400 is equal to 0.9% of the weight of the silver plating solution a.

The preparation method of the graphene-nicotinic acid silver plating solution comprises the following steps:

s1, dissolving silver salt, a complexing agent, a buffer solution, conductive salt and an additive into water to obtain electroplating solution;

s2, adding ammonia water into the electroplating solution to adjust the pH value to 10.2, and obtaining a silver plating solution a;

s3, adding graphene powder particles into 45% of the silver plating solution a, uniformly stirring, adding a dispersing agent, performing ultrasonic treatment for 25min, adding the rest silver plating solution a, uniformly stirring, and performing ultrasonic treatment for 25min again to obtain the silver plating solution.

The electroplating using conditions of the silver plating solution a are as follows: the current density of the electroplating is 0.28A/dm²The electroplating time is 48min, and the temperature is 28 ℃.

Experimental example 1 dispersant screening

First, a first screening experiment of the dispersant

1. Experimental samples:

the sample solution is a nicotinic acid cyanide-free silver plating solution as a base solution, and the pH value is controlled by ammonia water. The nicotinic acid cyanide-free silver plating solution is prepared from silver nitrate, nicotinic acid, ammonium acetate, potassium carbonate, potassium hydroxide and ammonia water, and the dosage ratio of each component refers to example 3 except that graphene is not contained.

Dividing the base liquid into four groups, wherein each group contains 100 ml of base liquid, and adding the following components:

group A: 50mg of graphene and 5mg of sodium dodecylbenzenesulfonate;

group B: 50mg graphene +5mg sodium dodecyl sulfate;

group C: 50mg graphene +5mg cetyltrimethylammonium bromide;

group D: 50mg of graphene and 5mg of sodium dodecyl sulfate;

2. observation record

0 min: all have no obvious change;

10 min: each group is uniformly dispersed solution through visual observation;

20 min: each group is uniformly dispersed solution through visual observation;

30 min: each group is uniformly dispersed solution through visual observation;

and (4) 40 min: the groups A, B and C have the tendency of sedimentation through light transmission observation, but the groups A, B and C are still uniformly dispersed through normal observation, and the group D is not light transmission and is in a uniformly dispersed solution state;

50 min: the groups A and C have macroscopic sedimentation tendency, but only have obvious sedimentation,

the condition of group B is slightly better than that of group D, and the group D is still uniform;

and (5) 60 min: the group A and the group C have obvious settlement, the group B has no obvious settlement, and the deposition is fluffy

And the group D is still uniform.

3. Conclusion of analysis

After one hour sedimentation observation, the analysis concluded: when only one dispersant is added, the dispersing effect is as follows: group D > group B > group C > group a.

Second, second screening experiment of dispersant

On the basis of a first screening experiment of the dispersing agent, three groups of reagents with better dispersing effect are selected, and the aim of verifying whether the dispersing effect can be improved by combining two reagents is fulfilled.

1. Experimental samples:

the sample solution is a nicotinic acid cyanide-free silver plating solution as a base solution, and the pH value is controlled by ammonia water. The nicotinic acid cyanide-free silver plating solution is prepared from silver nitrate, nicotinic acid, ammonium acetate, potassium carbonate, potassium hydroxide and ammonia water, and the dosage ratio of each component refers to example 3 except that graphene is not contained.

The base solution was divided into three groups, each group containing 100 ml of base solution, to which the following ingredients were added:

group A-1: 50mg of graphene, 3mg of sodium dodecyl sulfate and 3mg of sodium dodecyl sulfate;

group B-1: 50mg of graphene, 3mg of sodium dodecyl sulfate and 3mg of hexadecyl trimethyl ammonium bromide;

group C-1: 50mg graphene +3mg sodium dodecyl sulfate +3mg cetyltrimethylammonium bromide;

2. observation record

0 min: all have no obvious change;

10 min: the group C-1 has macroscopic deposition, is similar to the group B and is fluffy, and the rest groups are uniformly dispersed solution;

20 min: c-1 deposition is more obvious, and the rest groups are uniformly dispersed solution;

30 min: the B-1 group has a tendency of sedimentation under transparent observation, but is very unobvious;

and (4) 40 min: relatively unchanged;

50 min: relatively unchanged;

and (5) 60 min: b-1 is partially precipitated, and A-1 is still uniformly dispersed and light-proof.

3. Conclusion of analysis

After one hour sedimentation observation, the analysis concluded: when two dispersants are added, the best dispersing effect is compounded sodium dodecyl sulfate and sodium dodecyl sulfate. Therefore, the two dispersants were selected for further examination.

Third, third screening experiment of dispersant

1. Experimental samples:

the sample solution is a nicotinic acid cyanide-free silver plating solution as a base solution, and the pH value is controlled by ammonia water. The nicotinic acid cyanide-free silver plating solution is prepared from silver nitrate, nicotinic acid, ammonium acetate, potassium carbonate, potassium hydroxide and ammonia water, and the dosage ratio of each component refers to example 3 except that graphene is not contained.

The base solution was divided into three groups, each group containing 100 ml of base solution, to which the following ingredients were added:

a group: 50mg of graphene, 3mg of sodium dodecyl sulfate and 3mg of sodium dodecyl sulfate;

b group: 50mg of graphene;

and c, group: 50mg of graphene +3mg of sodium dodecyl sulfate;

and d, group: 50mg graphene +3mg sodium dodecyl sulphate.

2. Copper plate dispersion angle experiment:

each set of test samples was sampled with a test tube and dropped on a copper plate, and the contact angle thereof is shown in FIG. 1. The contact angles of the plating solutions of the experimental groups a, b, C and d on the copper plate are 19.428 degrees, 57.381 degrees, 49.848 degrees and 44.564 degrees respectively, and the contact angle of the experimental group a is far smaller than that of the experimental groups b, C and d, so that the dispersant prepared by compounding the sodium dodecyl sulfate and the sodium dodecyl sulfate has a better graphene dispersing effect.

3. Zeta potential test

The results of the Zeta potential test of the plating solutions of the experimental groups a, b, c and d are shown in FIG. 2. As can be seen from FIG. 2, the plating solutions of experimental groups a, b, c, d had Zeta potentials of 30.3mV, 1.4mV, 19.2mV, 12.7mV, and D, respectively. The higher the absolute value of Zeta potential, the better the dispersion of the venom, so the combination of sodium dodecyl sulfate and sodium dodecyl sulfate used in the invention has the most good dispersion effect.

Experimental example 2

1. Comparison of coating morphology prepared from pure silver plating solution and silver-graphene plating solution

The silver-graphene plating solution prepared in example 3 of the present invention was used to plate on a copper plate, and the plating morphology is shown in fig. 3, in which (a) shows a pure silver plating layer without graphene, and (b) shows a silver-graphene plating layer, compared with a sample obtained by plating a pure silver plating solution on a copper plate. As can be seen from the (a) picture and the (b) picture, the plating layers are uniformly distributed, wherein the silver-graphene plating solution on the (b) picture is uniformly distributed on the surface of the silver metal, and obvious particle shedding and hole structure defects do not exist.

2. Coating surface graphene verification

Verification 1: in order to verify whether the surface of the plating layer contains graphene or not, raman and energy spectrum analysis is performed on one of the raised structures of the plating layer shown in the graph (b) in fig. 3, and as a result, as shown in fig. 4, it is found that the element content of C reaches 8.75 wt%, and a raman spectrum also has a distinct characteristic peak of graphene, which can be proved that the introduced second-phase particles of graphene are part of the surface of the plating layer.

And (3) verification 2: in order to verify whether the interior of the plating layer contains graphene, the plating layer (b) in fig. 3 is polished by using P2000 sandpaper, and is cleaned by pure water after being polished, and is placed in absolute ethyl alcohol for 5min, and the EDS energy spectrum of the surface is shown in fig. 5, and the content of C is 5.79%, which can be proved to be the part of the introduced graphene second-phase particles in the interior of the plating layer.

Experimental example 3 comparative experiment of plating Properties

The silver-graphene coating of example 3 was compared to a succinimide cyanide-free silver coating containing graphene. Wherein, the silver plating solution used for the succinimide cyanide-free silver plating layer comprises the following components: 500g of silver nitrate; 1000g of succinimide; 1000g of potassium pyrophosphate; 300g of potassium hydroxide.

The specific experimental conditions were as follows:

1. anti-discoloration capability of plating solution

As shown in fig. 6, which shows the visual appearance of (a) the plating layer of example 3 of the present invention and (b) the succinimide plating layer after being left indoors for 72 hours, it can be seen from fig. 6 that the plating layer of example 3 of the present invention has a smoother surface without any visible oxidation, while the succinimide plating layer has been slightly yellowish.

2. Graphene dispersancy

Fig. 7 shows raman spectra of graphene on the surface of the coating layer after (a) the coating layer of the embodiment 3 of the present invention and (b) the succinimide coating layer are prepared as a composite coating layer.

The disappearance of the 2D peak in fig. 7, panel (b), in the Raman spectrum of the composite coating is probably due to the partial agglomeration of the graphene sheets during the co-deposition of the succinimide system, resulting in the multilayer graphene in the composite coating.

In the nicotinic acid silvering system shown in the graph (a) in fig. 7, the characteristic peak of graphene on the surface of the coating is obvious, and no obvious agglomeration phenomenon exists. This shows that the dispersibility of the present invention is more excellent.

3. Comparison of wear resistance of silver plating

As shown in fig. 8, respectively: (a) the method comprises the following steps of 3, a nicotinic acid graphene silver plating system, (b) a succinimide graphene silver plating system, and (c) the nicotinic acid silver plating system without graphene is a grinding trace on a UMT (unified modeling test) friction wear tester, wherein the load is 5N, the diameter of a steel ball is 6-6.5mm, the stroke is 1mm, and the frequency is 5 Hz.

The nicotinic acid silver plating system without graphene is prepared from silver nitrate, nicotinic acid, ammonium acetate, potassium carbonate, potassium hydroxide and ammonia water, and the dosage ratio of the components refers to example 3 except that graphene is not added.

As is evident from fig. 8, (a) the composite plating prepared by the silver plating solution of the present invention has a smaller wear area, an average wear scar width of only 190 μm, and an average wear scar depth of only 0.54 μm; the average width of the grinding trace of the composite plating layer prepared by the succinimide silver plating solution of the group (b) is only 210 mu m, and the average depth of the grinding trace is only 0.77 mu m; (c) the average grinding crack width of the composite plating layer prepared by the nicotinic acid silver plating solution without adding graphene reaches 240 mu m, and the average grinding crack depth reaches 1.22 mu m. Therefore, the composite plating layer prepared by the silver plating solution has better wear resistance.

4. Ablation resistance

As shown in fig. 9, respectively: (a) the embodiment 3 of the invention relates to a nicotinic acid graphene silver plating system, (b) a succinimide graphene silver plating system, and (c) the nicotinic acid silver plating system without graphene is used for the contact surface condition after the on-off current intensity is 10000A, the load is 10N, and 10000 times of on-off.

As is evident from fig. 9: (a) the ablation effect of the group (a) and the group (b) is better than that of the group (c); (b) the group had been completely burned through and exposed to the copper-based metal layer, and surface oxidation was more severe than in group (a). The composite coating prepared by the plating solution of the embodiment 3 of the invention has smaller ablation area, lower oxidation degree and no obvious burn-through mark.

Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of this invention as claimed.