Brush plating process and study on corrosion resistance and hardness of modified graphene on copper-based silver-graphene composite coating

Abstract

Electrical contact material is the key to the work of isolation switch electrical system. The sterling silver coating often used cannot meet the current requirements of power transmission equipment because of contact heat caused by oxidation and wear, corrosion resistance and wear resistance. In this paper, graphene was added to silver brush plating bath to prepare graphene uniformly suspended silver-graphene composite plating bath, and silver-graphene composite coating was prepared on pure copper by brush plating technology. The optimum process parameters of silver-graphene composite coating were obtained by adjusting brush plating voltage and brush plating time. The results show that the self-corrosion potential of silver-graphene composite coating is slightly lower than that of pure silver coating, and the self-corrosion current is lower, indicating that the corrosion resistance of silver-graphene composite coating is better. Under different brush plating voltages, the coating shows the most positive corrosion potential and the lowest self-corrosion current density at 3V, and the corrosion resistance is the best at 2min under different brush plating time. When the graphene content is 30g/L, the binding rate between graphene and silver coating is the highest, the thickness of the coating is 23.5μm.

Keywords:
Brush plating; Silver-graphene composite coating; Corrosion resistance; Electrical contact materials

1. INTRODUCTION

At present, there are a large number of electrical contact parts of electrical equipment in the power grid (high voltage isolation switch, junction board, bus joint, wire clamp, etc.). According to incomplete statistics, about half of the electrical contact parts have the phenomena of overheating [¹,²,³], excessive contact resistance and so on. The surface of these electrical contact parts has obvious burning and welding morphology, and even burned out in serious cases. The main causes of heating of electrical contact parts are surface corrosion, wear, shedding, etc., resulting in an increase in contact resistance and a sudden increase in heat generation at the contact part [⁴, ⁵].

The isolation switch undertakes the tasks of transfer, isolation, turning on and breaking, and the contact finger is one of its core components. In order to prevent the contact finger of the isolation switch from peroxidation [⁶] and improve the electrical conductivity and current capacity of the contact part of the contact, the contact of the isolation switch should be treated with silver plating [⁷]. However, the isolation switch is an open type, which is greatly affected by environmental factors, coupled with a large number of separation and closing operations and arc erosion in operation [⁸], the common silver-plating layer is easy to peel off prematurely and expose copper, resulting in frequent occurrence of various defects in electrical contact materials [⁹]. It threatens the operation safety of the power grid. Ordinary silver-plating layer has been difficult to meet the needs of practical applications, so it is urgent to develop a new type of silver-based coating with excellent comprehensive properties.

The silver-plating process has two systems: cyanide silver plating and cyanide-free silver plating. Silver cyanide plating has the advantages of stable bath, fine and bright coating and good adhesion, so it has always occupied a leading position in practical production. However, cyanide is extremely toxic, which does great harm to the ecological environment and the health of production personnel, and requires high technology and cost for the treatment of waste liquid, so scholars at home and abroad have conducted extensive and in-depth research on cyanide-free silver plating [¹⁰] for a long time. It is expected that cyanide-free silver plating can be used to replace cyanide silver plating [¹¹,¹²,¹³]. At present, the main cyanide-free silver-plating systems at home and abroad include succinimide silver plating [¹⁴,¹⁵,¹⁶,¹⁷,¹⁸], thiosulfate silver plating [¹⁹,²⁰,²¹,²²,²³], sulfite silver plating, 5-dimethylhydantoin, iodide silver plating and so on.

Point contact parts are easy to be ablated by arc in the process of opening and closing. To improve the arc stability, contact performance, and lifespan of electrical contacts, B2O3 may be used to form ternary or complex composites [²⁴]. The composite can remove the non-conductive MeO film formed during the arc corrosion test, thus improving the arc stability. In the point contact, the arc ablation degree of the dynamic and static contact is different. In the study of the influence of different current loads on the arc ablation performance of electrical contacts, In the study of the influence of different current loads on the arc ablation performance of electrical contacts [²⁵].

A new type of copper-based functionally graded electrical contact material composed of silver-plated [²⁶], nickel-plated and chromium-plated copper core particles was fabricated by hot pressing technology. Used to manufacture functionally graded materials (FGM) by hot pressing; pure copper, two-layer and three-layer metal powders are used in the lower, middle and upper layers, respectively. Compared with pure copper, the wear and arc corrosion properties of the developed materials are improved by 3 to 10 times. Wear tests show that the abrasive wear mechanism is the main factor of FGMs, including chemical nickel and chromium coatings.

Silver and graphite [²⁷] with good electrical conductivity are co-deposited, and the silver-graphite composite coating has both electrical contact function and self-lubricity. This composite coating is widely used in the electrical contact parts of high voltage switches. Siemens of Germany first developed silver-graphite composite electrical contact material in cyanide silver plating system, which can significantly prolong its service life [²⁸,²⁹,³⁰] when used in the contact finger part of the disconnector. On this basis, pure silver/silver-graphite composite coating was prepared by BIN et al. [³¹]. They first plated pure silver on the substrate, and then carried out silver-graphite composite plating. Due to the existence of the diffusion layer on the surface of the cathode and the tip discharge effect of graphite, the growth mode of silver in the coating is spherical to massive, and then from massive to island. However, cyanide is so toxic that it has been banned in many countries. Therefore, the preparation of silver-graphite composite coating without cyanide has attracted more and more attention. TONG et al. [³²] studied the effect of nano-graphite (50~80 nm) on cyanide-free brush silver plating. The results show that the addition of nano-graphite can significantly increase the electrodeposition rate, increase the hardness and compactness of the coating, and does not affect the appearance of the coating. The study of WANG et al. [³³] shows that carbon can slow down the vulcanization reaction of silver, and the sulfidation resistance of silver-graphite composite coating is significantly improved by adding graphite powder to cyanide-free silver-plating solution.

To sum up, this paper attempts to introduce graphene as the second phase into the silver-based composite coating [³⁴, ³⁵], hoping that graphene can improve the related properties of the silver-based composite coating [³⁶, ³⁷]. At present, the traditional powder metallurgy method is mostly used in the research on the composite of graphene and metal silver, which requires high process equipment and complex reaction process. The study on the preparation of silver-graphene composite coating by brush plating is rare. Therefore, a series of exploratory attempts on the preparation, characterization and properties of silver-graphene composite coatings not only promote the research and development of composite electrical contact materials for isolators, but also provide new ideas and methods for the application of graphene in metal matrix composites, and provide a certain experimental and theoretical basis for the development and application of graphene reinforced metal matrix composites.

2. EXPERIMENTS

2.1. Reagents and materials

Silver nitrate is purchased from Fuchen (Tianjin) Chemical Reagent Co., Ltd., succinimide is purchased from Beijing Ballingway Technology Co., Ltd., graphene (6–15 layers) and graphene dispersant are purchased from Shanghai McLean biochemical Technology Co., Ltd., potassium pyrophosphate is purchased from Shanghai Merrill biochemical Technology Co., Ltd., electric purification solution and activation solution are purchased from Zhongke Nano Times Co., Ltd., pure copper purity 99.9%, size 50 mm × 30 mm × 1 mm Purchased from Shenzhen Quanfu Metal Co., Ltd.

2.2. Preparation of composite coating

Surface pretreatment: the pure copper with the size of 30 mm × 100 mm × 1 mm was used as the substrate. First of all, the copper-based surface is polished with 800 mesh, 1000 mesh and 1200 mesh sandpaper to remove dirt and oxides to ensure that the sample is bright and free of rust. Then, the sample 1~2min was soaked in 50% hydrochloric acid at 60 °C, 70 °C and 5~10min, followed by NaOH 2~5g/L, Na2SO4 35~55g/L, Na2CO3 30~50g/L, Na2SiO3 10~20g/L and deionized water. The purpose is to remove the oxide from the surface of the sample and produce slight etching, which is beneficial to the deposition of silver and the improvement of the adhesion between the substrate and the coating.

Electrical purification: electrical purification of polished copper substrates to dissolve grease and oil stains on the surface. The brush plating voltage of 8V~12V is used to purify the surface, and the brush plating time is 30–40s.

Activation: the oxide film and fatigue layer on the surface of the substrate are removed by activation treatment. Brush plating voltage from −12V to −8V select 30–40s.

Preparation of pure silver coating: prepare the silver plating solution of 100ml, use the brush plating machine for brush plating, connect the copper substrate to the negative electrode of the power supply as the cathode, and the plating pen (with jacket) connected to the positive pole of the power supply is dipped in the plating solution as the anode, relying on the role of DC current, through the plating pen to maintain contact with the workpiece at a certain pressure and make relative movement, the metal silver ions in the plating solution will discharge and crystallize on the workpiece as the cathode to form a sterling silver coating. After brushing, rinse with water, then rinse with alcohol, finally blow-dry and pack, and so on, use the high-frequency mechanical vibration of the ultrasonic cleaning machine to clean the impurities on the surface of the sample wrapped in oil and adhere to the solid surface and clean the fingerprints attached to the surface.

Preparation of silver-graphene composite coating: adding 20mg graphene powder to the silver-plating solution of 100ml, graphene will agglomerate because of electrostatic action, and the graphene will be uniformly dispersed in the solution by magnetic mixer. Using the brush plating machine for brush plating, firstly, the copper plating substrate is connected to the negative electrode of the power supply as the cathode, and the plating pen (with jacket) connected to the positive pole of the power supply is dipped in the plating solution as the anode, relying on the action of direct current. Through the plating pen to maintain contact with the workpiece at a certain pressure and make relative movement during brush plating, the metal cations in the bath will discharge and crystallize on the workpiece as the cathode to form a composite coating.

2.3. Microstructure observation

The phase composition of the coating was analyzed by X-ray diffractometer (PHILIPS X-Pert MPD, Anhui Guoke instrument Technology Co., Ltd., Netherlands, XRD). The graphene and silver-graphite composite coatings treated by 532 nm laser were characterized by laser confocal Raman spectroscopy (Horiba Science Labram HR Evolution, Keynes (China) Co., Ltd., Raman, Japan). Observe the sample to be observed under the metallographic microscope, and then the surface morphology and microstructure were characterized by scanning electron microscope (PHLIPSL30W/TMP, Anhui Guoke instrument Technology Co., Ltd., Netherlands, SEM) and energy dispersive spectroscopy (FD-3022-I, Spike Technology Co., Germany, EMPA).

2.4. Microhardness test

In this experiment, the hardness of the sample was tested by a fully automatic microhardness tester equipped with automatic test force conversion and built-in CCD and XY sample tables. Its indenter is a positive square cone diamond indenter with a diagonal angle of 136°, which can be used to test the hardness of thin metal, fine wire and surface hardened layer, coating and coating. Table 1 shows the hardness data of silver-graphene and pure silver brush coatings under different conditions.

Table 1
Three types of quality loss roughness.

COATING LAYER	GRAPHENE ADDITION (g/L)	BRUSH PLATING VOLTAGE (V)	BRUSH PLATING TIME (min)	HARDNESS (HV)
Pure Ag	0	3	2	129.6
Ag-GE	5			98.6
	10			104.8
	15			118.2
	20			127.8
	25			136
	30			138.4

2.5. Corrosion resistance test

Using 3.5 wt.% NaCl solution as corrosion medium, the Tafel polarization curve and AC impedance spectrum of the coating was measured by electrochemical workstation CHI660E with standard three electrodes to analyze the corrosion resistance of the coating, in which saturated calomel electrode was used as reference electrode, platinum electrode as auxiliary electrode and 10 mm × 10 mm × 1 mm copper-based coating sample as working electrode at 25 °C.

3. RESULTS AND DISCUSSION

3.1. Microstructure characterization

Figure 1 shows the principal diagram of the formation of the copper-based silver-graphene composite coating and the XRD, Raman, SEM and EDS diagrams characterizing the composition of the composite coating.

Figure 1
(a) (b) schematic diagram of Ag-G composite coating prepared by composite brush plating; (c) X-ray diffraction pattern; (d) Raman spectrum; (e) (f) SEM diagram; (g) (h) EDS diagram.

Figure 1(a)-(b) shows the schematic diagram of composite brush plating. When brushing is carried out with an electric brush plating machine, firstly, the negative electrode of the power supply is connected to the copper plating substrate as the cathode, and the plating pen (with sheath) connected to the positive pole of the power supply is dipped into the plating bath as the anode. Depending on the action of direct current, the metal cations in the plating solution will discharge and crystallize on the workpiece as the cathode through the brush plating pen keeping contact with the workpiece at a certain pressure and making relative movement. To form a composite coating. In the process of composite brush plating, Graphene is uniformly distributed in the silver-plating layer [³⁸, ³⁹].

Figure 1(c) shows the XRD diagram of the composite coating with graphene addition of 5, 10, 15, 20, 25 and 30 g/L. Compared with the above six groups of data, it can be seen that all the coatings have obvious diffraction peaks at 2θ = 38.106°, 44.298°, 51.116°, 64.504°, 74.286°, 78.851°. The comparison of PDF cards is in good agreement with Silver-3C, and the dominant growth surface is (111) [⁴⁰]. Compared with the diffraction peaks of six kinds of graphene content, the silver-graphene composite coating with graphene content of 15g/L has good adhesion with the substrate. The characteristic peak of graphene was not observed in the six groups of silver-graphene composite coatings, because the content of graphene in the bath was not high, and the graphene entering the silver coating was less, so the characteristic peak of graphene was not detected. The diffraction peaks of six kinds of silver-graphene composite coatings all appear Cu, this is because the coating is thin and the copper substrate is detected. Finally, there is no obvious diffraction peak of other elements except Ag, Cu and C in the XRD diffraction peak, which indicates that the content of other impurity phases in the silver-graphene composite coating is low.

Figure 1(d) shows the Raman spectra of graphene and silver-G composite coatings. As can be seen from the figure, the Ag-G composite coating shows a typical D peak of graphene defects (1351 cm⁻¹), a G peak vibrating in the sp2 carbon atom plane (1585 cm⁻¹), and a carbon atom packing mode 2D peak (2928 cm⁻¹). The defect degree of graphene is usually evaluated by the ratio of D peak to G peak intensity [⁴¹,⁴²,⁴³,⁴⁴]. The ID/ IG values of graphene and Ag-G composite coatings are 0.66 and 1.02 respectively, indicating that graphene is added to the Ag-G composite coating and the defect density is low. In addition, compared with graphene, the Raman characteristic peak of Ag-G composite coating has a smaller high frequency shift, which may be the result of composite [⁴⁵].

Figure 1(e-f) show the surface scanning images of 500× and 20000× observed by scanning electron microscope. The particles in the coating are closely arranged and uniform in size, and the silver particles wrap graphene to form a granular spherical substance [⁴⁶]. Figure 1(g-h) are EDS diagrams of the composite coating. As shown in the figure, there are obvious diffraction peaks of silver and carbon in the silver-graphene composite coating, in which the diffraction peak of silver is the strongest and the content of carbon is relatively less, which may be due to the low content of graphene in the coating, so the carbon peak in the energy spectrum is weak. Through the analysis of the distribution diagram of silver and carbon elements in the silver-graphene composite coating, for example, the distribution of silver elements in the coating shows a uniform green lattice, and the orange dot in the picture represents the distribution of carbon elements in the coating. It can be seen that silver and graphene are uniformly distributed in the coating without obvious agglomeration, which shows that the brush plating process used in this experiment can prepare uniform dispersion. It can be found that the carbon content in the silver-graphene composite coating is 17.96%, which proves the existence of graphene in the silver-graphene composite coating.

3.2. Analysis of microhardness of coating

As can be seen from Table 1, the average hardness of sterling silver plating is 129.6HV. The average hardness of silver-graphene composite coating increases with the increase of graphene content, and when the graphene content reaches 25g/L, the hardness of silver-graphene composite coating no longer increases obviously with the increase of graphene content. The average hardness of pure silver coating is slightly higher than that of graphene 20g/L.

As the graphene content increases, the binding efficiency of graphene particles will change. When the si lver coating increases, graphene can be uniformly dispersed in the silver coating and exist in the form of inclusi ons in the silver. This type of coating in the form of a package has a certain blocking effect on dislocation moti on and plasticity, which can restrict the flow of particles [⁴⁷, ⁴⁸]. Therefore, the addition of graphene increases, the strengthening effect is enhanced, and the hardness increases. When the amount of graphene reaches 25g/L, the binding between graphene particles and silver coating is close to saturation, the strengthening effect changes little, and the hardness no longer increases obviously.

As a reinforcing phase, graphene is an ideal material for stress exchange with matrix because of its unique geometric shape and two-dimensional flake structure. At present, the strengthening mechanisms of graphene reinforced metal matrix composites mainly include load transfer mechanism, dislocation strengthening, fine grain strengthening and so on. According to the different process conditions, various strengthening mechanisms cooperate to strengthen the matrix, rather than a single effect, so the hardness of the coating should be improved after the addition of graphene.

First of all, agglomeration makes its dispersion in the composites uneven, thus affecting the properties of the composites. Secondly, the agglomerated graphene will form a lot of resistance in the process of transport and separation, which will reduce the transmission efficiency and separation effect of graphene. Therefore, the hardness of silver-graphene composite coating decreases rather than increases due to the agglomeration of graphene.

3.3. Corrosion resistance test of coating

As shown in Table 2, by comparing the different process conditions of brush plating time and voltage, the composite coating has more positive self-corrosion potential, lower self-corrosion current density and better corrosion resistance than pure silver plating.

Table 2
Self-corrosion potential and self-corrosion current density of silver-graphene and pure silver brush coatings under different conditions.

COATING LAYER	BRUSH PLATING VOLTAGE (V)	BRUSH PLATING TIME (min)	SELF-CORROSION POTENTIAL (V)	SELF-CORROSION CURRENT DENSITY (A/cm2)
Ag-GE	3	2	−0.116	4.694×e-7
		3	−0.111	5.399×e-7
		4	−0.191	2.813×e-6
	4	2	−0.185	3.747×e-6
		3	−0.129	4.180×e-6
		4	−0.126	9.560×e-6
	5	2	−0.156	5.462×e-6
		3	−0.121	3.828×e-6
		4	−0.126	6.424×e-6
Pure Ag	3	2	−0.137	2.574×e-6
	4		−0.132	3.996×e-6
	5		−0.133	6.634×e-6

The potentiodynamic polarization curves of silver coating and silver-graphene composite coating in 3.5%NaCl solution are shown in Figure 2(a). For electrochemical corrosion, the corrosion potential can indicate the corrosion tendency of the alloy, and the self-corrosion current density can be used to indicate the corrosion rate. Compared with pure silver coating, the potentiodynamic polarization curve of silver-graphene composite coating in 3.5%NaCl solution shows lower self-corrosion potential, which indicates that the initial corrosion potential of silver-graphene composite coating is more negative, that is, it is easier to start corrosion. However, the self-corrosion current of the silver-graphene composite coating is lower than that of the pure silver coating, which means that the corrosion rate is slower, indicating that the corrosion resistance of the composite coating is improved. This phenomenon can be attributed to the addition of graphene. The codeposition of graphene and silver into the composite coating not only increases the compactness of the coating,but also can uniformly adhere to the grains to form a protective film because of the chemical stability and high hydrophobicity of graphene itself. Properly isolate the direct contact between the corrosion medium and the grain or grain boundary. So as to improve the corrosion resistance of the composite coating. The potentiodynamic polarization curve of silver-graphene composite coating in 3.5%NaCl solution under different brush plating voltage is shown in Figure 2(b). It can be found that the corrosion potential of silver-graphene composite coating is the most positive and the corrosion tendency is the lowest when the brush plating voltage is 3V in the same brush plating time, and the corrosion current density is also the lowest when the brush plating voltage is 3V, indicating that the sample has the best corrosion resistance when the brush plating voltage is 3V. The potentiodynamic polarization curve of silver-graphene composite coating in 3.5%NaCl solution under different brush plating time is shown in Figure 2(c). It can be found that under the same brush plating voltage, the longer the brush plating time is, the greater the corrosion tendency is, and the corrosion is faster, so the corrosion resistance of the sample is the best in 2min.

Figure 2
Schematic diagram of Tafel polarization curve of coating: a) comparison of Tafel polarization curve of different coatings; b) comparison of Tafel polarization curves for different brush plating voltages; c) comparison of Tafel polarization curves for different brush plating times.

3.4. Analysis of AC impedance spectrum of coating

The Nyquist diagram and Bode diagram are drawn according to the impedance spectrum test results of the composite coating. The Nyquist diagram is based on the impedance imaginary part (−Z”) to the real part (Z’) of the impedance. The larger the arc radius in the figure is, the greater the polarization resistance is, the better the corrosion resistance is. It can be seen from Figure 3(a) that the silver-graphene composite coating shows higher impedance when the brush plating voltage is 3V and the brush plating time is 2min and 3min. It can be inferred that the samples under these two process conditions have good corrosion resistance. As can be seen from the logarithmic diagram of Figure 3(b) Bode impedance modulus |Z| and frequency f, the composite coatings with brush plating voltage 3V and brush plating time 2min and 3min have higher impedance modulus in the low frequency region. At present, the lowest frequency impedance modulus (|Z| 0.01Hz) is generally selected as the standard to evaluate the protective performance of the coating. |Z| the higher the 0.01Hz value, the better the corrosion resistance, and vice versa. So, the change trend of |Z| 0.01Hz is consistent with the phenomenon reflected in the Nyquist chart. The logarithmic diagram of Bode phase angle and frequency also shows that the phase angle of the composite coating with 3V brush plating voltage, 2min and 3min brush plating time is significantly higher than that of other process conditions, indicating that the composite coating has better corrosion resistance when the brush plating voltage is 3V and the brush plating time is 2min and 3min. Figure 3(d) is based on the equivalent circuit model R (QR (OR)) in ZSimpWin software.

Figure 3
Impedance diagram of silver-graphene composite coating: a) Nyquist diagram; b) bode modulus diagram; c) is bode phase angle diagram; d) is equivalent circuit schematic diagram.

3.5. The influence of different brush plating processes on coating thickness

As shown in Figure 4, when the graphene addition is 5-25g/L, the thickness of the composite coating increases continuously, the coating surface of 5g/L and 15g/L is zigzag and uneven, the coating surface of 25g/L tends to be flat, and the pores inside the coating are the least, which represents that the combination rate of 25g/L graphene and silver plating layer is high, and the porosity is low, which also organizes the external corrosion medium to enter the silver plating layer, improving the corrosion resistance of the composite coating. When the amount of graphene is added to 30g/L, although the thickness of the coating increases, the surface coating becomes uneven and the porosity increases, which may be due to the decrease of adhesion and partial shedding of the composite coating.

Figure 4
a, b, c and d are cross-sectional views of silver-graphene composite coatings with graphene content of 5, 15, 25 and 30g/L, respectively.

As shown in Table 3, the thickness of silver-graphene composite coating increases with the increase of graphene content. Some studies show that with the increase of graphene content in the bath, the graphene content in the composite coating increases rapidly, but when the graphene content reaches a certain extent, the growth rate slows down. In this process, the wear resistance and thermal conductivity of the composite coating are continuously improved, while the hardness and surface contact resistance change little. This shows that in a certain range, increasing the thickness of the coating can improve the wear resistance, but when the saturation point is reached, the effect of increasing the thickness of the coating on the wear resistance is limited.

Table 3
Coating thickness.

GRAPHENE ADDITION (g/L)	BRUSH PLATING VOLTAGE (V)	BRUSH PLATING TIME (min)	COATING THICKNESS (μm)
5	3	2	9.1
15			16.2
25			20.1
30			23.5

4. CONCLUSIONS

Silver-graphene composite coating was successfully prepared by brush plating in cyanide-free composite electrolyte. Compared with the sterling silver coating, the graphene in the composite coating has uniform dispersion, high hardness and fine microstructure. The following conclusions were drawn:

• (1)

  From the micro-morphology and energy spectrum of silver-graphene composite coating, it can be seen that the cyanide-free brush plating process can prepare silver-graphene composite coating with good dispersibility and adhesion. The cross-section thickness of the coating can reach more than 20μm and is uniform, and the experimental brush plating effect is good.

• (2)

  With the increase of voltage and time, the coating becomes more compact and the grain size decreases. Through electrochemical test and analysis, the self-corrosion potential of silver-graphene composite coating is slightly lower than that of pure silver coating, and the self-corrosion current is lower, indicating that the corrosion resistance of silver-graphene composite coating is better.

• (3)

  In the Nyquist diagram, the silver-graphene composite coating shows a higher impedance value, the lowest frequency impedance modulus (|Z| 0.01Hz) is also higher in the Bode diagram, and the phase angle is also higher than that of the coating under other process conditions, indicating that the composite coating has better corrosion resistance. Especially suitable for on-site repair.

5. ACKNOWLEDGMENTS

This work was supported by the Science and Technology Project of State Grid Jibei Electric Power Co., Ltd. Tangshan Power supply Company. The name of the project is the research and application of composite silver plating heating treatment technology for power transmission and transformation equipment. The project number is B3010323001D.

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Publication Dates

• Publication in this collection
  21 Oct 2024
• Date of issue
  2024

History

• Received
  27 July 2024
• Accepted
  28 Aug 2024