Chemical nickel plating solution based on synergistic effect of multiple complexing agents and preparation method of chemical nickel plating solution

Abstract

The invention relates to the technical field of chemical nickel plating, and discloses a chemical nickel plating solution based on the synergistic effect of a multi-element complexing agent and a preparation method thereof.The chemical nickel plating solution comprises, by weight, 20-35 parts of nickel salt, 25-40 parts of sodium hypophosphite, 30-48 parts of the multi-element complexing agent, 0.1-5 parts of a stabilizer, 0.5-3 parts of a surfactant and the balance deionized water; wherein the multi-element complexing agent comprises an organic complexing agent and nanoparticles, the organic complexing agent comprises a weak complexing agent and a strong complexing agent, and the nanoparticles comprise silicon dioxide or carbon quantum dots. A weak complexing agent and a strong complexing agent are added step by step in a gradient mode, surface functionalized nano-particles are combined, the weak complexing agent is preferentially combined with nickel ions to promote rapid nucleation of a plating layer, the strong complexing agent later enhances complexing stability, the nano-particles provide heterogeneous nucleation sites and optimize the microstructure of the plating layer, and the surface functionalized nano-particles are formed. Therefore, densification, low porosity and high mechanical performance of the plating layer are realized.

Description

Technical Field

[0001] The invention relates to the technical field of chemical nickel plating, in particular to a chemical nickel plating solution based on the synergistic effect of multiple complexing agents and a preparation method thereof. Background Art

[0002] In recent years, with the increasing demand for high-performance coatings in fields such as precision electronics and aerospace, chemical nickel plating technology has gradually evolved towards high uniformity, low defect rate and environmental friendliness. Chemical nickel plating technology has become one of the key processes in the field of surface engineering due to its excellent coating uniformity, corrosion resistance and the need for no external current. In recent years, the global manufacturing industry's demand for coating performance has gradually upgraded from single functionality to comprehensive performance such as high hardness, high wear resistance, low porosity and long life. At the same time, the deepening of green manufacturing and sustainable development concepts has further promoted the innovative iteration of chemical nickel plating solution formula design and process optimization technology. Traditional chemical nickel plating solutions mostly use a single chelating agent to stabilize nickel ions.

[0003] However, in current technology, a single complexing agent stabilizes nickel ions, but has low complexing efficiency and poor plating solution stability, resulting in high porosity and low hardness in the coating. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a chemical nickel plating solution based on the synergistic effect of multiple complexing agents and a preparation method thereof, which solves the problems of low complexing efficiency and poor stability of the plating solution, resulting in high porosity and low hardness of the coating.

[0005] To achieve the above objectives, the present invention is implemented by the following technical solution: a chemical nickel plating solution based on the synergistic effect of a multi-component complexing agent, comprising the following raw materials in parts by weight: 20-35 parts of a nickel salt, 25-40 parts of sodium hypophosphite, 30-48 parts of a multi-component complexing agent, 0.1-5 parts of a stabilizer, 0.5-3 parts of a surfactant, and the balance of ionized water;

[0006] The multi-component complexing agent includes an organic complexing agent and nanoparticles, the organic complexing agent includes a weak complexing agent and a strong complexing agent, and the nanoparticles include silicon dioxide or carbon quantum dots.

[0007] Preferably, the nanoparticles have a particle size of 1-100 nanometers, and are surface-modified with carboxyl or amino functional groups.

[0008] Preferably, the weak complexing agent includes lactic acid or malic acid, accounting for 10-15 parts, and the strong complexing agent includes citric acid or ethylenediaminetetraacetic acid, accounting for 20-30 parts;

[0009] The nanoparticles include silicon dioxide or carbon quantum dots, accounting for 1-2 parts.

[0010] Preferably, the stabilizer includes thiourea, rare earth salt and 2-mercaptobenzothiazole, the rare earth salt includes cerium salt, lanthanum salt or neodymium salt, and the rare earth salt accounts for 0.2-0.5 parts.

[0011] Preferably, the surfactant comprises an alkyl glycoside or a sophorolipid, and the molar ratio of the surfactant to citric acid is 1:10-1:20.

[0012] A method for preparing a chemical nickel plating solution based on the synergistic effect of multiple complexing agents, the method comprising the following steps:

[0013] S1, dissolving nickel salt in deionized water to obtain a nickel salt solution;

[0014] S2. performing low-temperature plasma activation treatment on the multi-component complexing agent;

[0015] S3, first add a weak complexing agent to the nickel salt solution, stir for 10 to 30 minutes, and then add a strong complexing agent and nanoparticles in sequence;

[0016] S4, adding sodium hypophosphite, stabilizer and surfactant, and stirring and mixing;

[0017] S5. Adjust the pH to 4.5-5.5, and obtain a chemical nickel plating solution after two-stage filtration.

[0018] Preferably, the power of the low-temperature plasma treatment in S1 is 80-100 W, the treatment time is 2-4 minutes, and the plasma gas includes a mixed gas of argon and oxygen, and the volume ratio of argon to oxygen is 9:1.

[0019] Preferably, in S3, the interval between adding the weak complexing agent and the strong complexing agent is 15 to 25 minutes, and the dissolution temperature of the weak complexing agent is 40-50°C, and the dissolution temperature of the strong complexing agent is 25-35°C.

[0020] Preferably, the pH is adjusted in S5 by a gradient adjustment method, first adjusting the pH to 5.0-5.5 with citric acid, then fine-tuning it to 4.5-5.0 with ammonia water, and controlling the temperature at 30-32°C.

[0021] Preferably, the two-stage filtration in S5 includes: pre-filtration, using a filter element with a pore size of 1-5 μm to remove large particle agglomerates;

[0022] Nanofiltration uses a filter element with a pore size of 0.1-0.5 μm to retain undispersed nanoparticle aggregates.

[0023] The invention provides a chemical nickel plating solution based on the synergistic effect of multiple complexing agents and a preparation method thereof.

[0024] It has the following beneficial effects:

[0025] 1. The present invention combines surface functionalized nanoparticles through the step-by-step gradient addition of weak complexing agents and strong complexing agents. The weak complexing agent preferentially binds to nickel ions to promote rapid nucleation of the coating, and the strong complexing agent subsequently enhances the complexation stability and inhibits side reactions. The nanoparticles provide heterogeneous nucleation sites and optimize the microstructure of the coating, thereby achieving densification, low porosity and high mechanical properties of the coating.

[0026] 2. The present invention combines temperature and time control through a step-by-step gradient complexation process. A weak complexing agent preferentially binds to nickel ions at high temperature. A strong complexing agent is introduced after an interval to form a dynamic complexation equilibrium. Nanoparticles are co-deposited on the coating, optimizing the nickel ion controlled release and heterogeneous nucleation effect, thereby increasing the nickel plating speed.

[0027] 3. The present invention treats a multi-component complexing agent with low-temperature plasma, utilizing high-energy particle bombardment and oxidative modification in a mixed atmosphere of argon and oxygen to selectively activate functional groups such as carboxyl and amino groups, significantly enhancing their ability to bind nickel ions. This reduces the amount of complexing agent used and lowers costs. The activated complexing agent also synergizes with nanoparticles and stabilizers to extend the life of the plating solution and enhance the corrosion resistance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a flow chart of a method for preparing a chemical nickel plating solution based on the synergistic effect of multiple complexing agents. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] Please see the attached Figure 1 The embodiment of the present invention provides an electroless nickel plating solution based on the synergistic effect of a multi-component complexing agent, comprising the following raw materials in parts by weight: 20-35 parts of a nickel salt, 25-40 parts of sodium hypophosphite, 30-48 parts of a multi-component complexing agent, 0.1-5 parts of a stabilizer, 0.5-3 parts of a surfactant, and the balance of ionized water;

[0031] The multi-component complexing agent includes an organic complexing agent and nanoparticles, the organic complexing agent includes a weak complexing agent and a strong complexing agent, and the nanoparticles include silicon dioxide or carbon quantum dots.

[0032] Specifically, the nickel salt provides nickel ions (Ni2) as the main salt, which deposits metallic nickel on the surface of the substrate through a reduction reaction to form a continuous plating layer, ensuring sufficient nickel ion supply and avoiding excessive nickel ions that cause instability in the plating solution;

[0033] Sodium hypophosphite acts as a reducing agent and decomposes under acidic or alkaline conditions, releasing active hydrogen atoms to convert Ni 2+ Reduced to metallic nickel, while self-oxidized to generate H2PO3 - , and release phosphorus atoms to participate in co-deposition, which can not only provide sufficient reducing power to drive the reaction, but also form an amorphous nickel-phosphorus alloy through phosphorus co-deposition, thereby improving the corrosion resistance and hardness of the coating;

[0034] Weak complexing agent in multi-component complexing agent and Ni 2+ Forming an unstable complex, Ni is released preferentially at the initial stage of the reaction 2+ , accelerate the coating nucleation and shorten the plating time; strong complexing agent: with Ni 2+ Form a stable complex to inhibit free Ni 2+ Concentration fluctuations prevent nickel salt from hydrolyzing and forming precipitation, thus extending the life of the plating solution; Nanoparticles: through chemical adsorption with Ni 2+ Combined with the nanoparticles, it provides heterogeneous nucleation sites, refines the coating grains to the nanoscale, and the nanoparticles are co-deposited to form a composite coating of nickel, phosphorus and nanoparticles, thereby improving the hardness of the coating and reducing the porosity; that is, the weak complexing agent and the strong complexing agent are added step by step to achieve Ni 2+ Dynamic sustained release of nanoparticles to enhance the functionality of the coating;

[0035] Stabilizers selectively inhibit side reactions through physical adsorption or chemical coordination, improve the stability of the plating solution at high temperatures, extend the self-decomposition time, and reduce the loss rate of ineffective nickel deposition;

[0036] Surfactants can reduce the surface tension of the plating solution, improve wettability, ensure sufficient spreading of the plating solution in complex substrates (such as blind holes and microgrooves), achieve uniform coverage within the microstructure of the coating, and enhance bonding strength.

[0037] The particle size of the nanoparticles is 1-100 nanometers, and the surface is modified with carboxyl or amino functional groups.

[0038] Specifically, nanoparticles optimize the performance of the plating solution and coating through chemical coordination and physical synergy. Their surface functional groups form stable coordination bonds with nickel ions, enhancing the directional anchoring ability of nickel ions. Simultaneously, through steric hindrance, they inhibit particle agglomeration and ensure uniform dispersion in the plating solution. Nanoparticles act as heterogeneous nucleation sites, promoting the refined deposition of nickel-phosphorus alloys and forming a dense and uniform coating microstructure. This combined effect significantly improves the mechanical strength and surface density of the coating, effectively reduces porosity defects, enhances the chemical stability of the plating solution, inhibits side reactions, and thus extends the service life of the process.

[0039] Weak complexing agents include lactic acid or malic acid, accounting for 10-15 parts, and strong complexing agents include citric acid or ethylenediaminetetraacetic acid, accounting for 20-30 parts;

[0040] Nanoparticles include silica or carbon quantum dots, accounting for 1-2 parts.

[0041] Specifically, weak chelating agents (lactic acid or malic acid) form moderately loose complexes with nickel ions, preferentially releasing nickel ions to promote the initial nucleation of the coating and ensure the deposition startup efficiency; strong chelating agents (citric acid or ethylenediaminetetraacetic acid) stabilize nickel ions through strong coordination, inhibit hydrolysis precipitation, and maintain the long-term stability of the plating solution. The two are added step by step to form a dynamic complexation equilibrium, which not only controls the reaction rate but also reduces the ineffective loss of nickel ions. The carboxyl or amino functional groups modified on the surface of the nanoparticles (silicon dioxide or carbon quantum dots) selectively combine with nickel ions, serving as heterogeneous nucleation sites to refine the coating grains, and at the same time enhance the density and mechanical properties of the coating through physical co-deposition, ultimately achieving a highly uniform, low-defect nickel-phosphorus alloy coating and significantly extending the service life of the plating solution.

[0042] The stabilizer includes thiourea, rare earth salt and 2-mercaptobenzothiazole. The rare earth salt includes cerium salt, lanthanum salt or neodymium salt, and the rare earth salt accounts for 0.2-0.5 parts.

[0043] Specifically, the stabilizer synergistically inhibits the spontaneous decomposition of the plating solution through multiple mechanisms. Thiourea preferentially adsorbs on the surface of active impurities, blocking their catalytic non-selective reduction of nickel ions. Rare earth salts (cerium salts, lanthanum salts or neodymium salts) form colloidal hydroxides in the plating solution, occupying microscopic defect sites of the substrate, inhibiting the plating porosity caused by hydrogen evolution. 2-mercaptobenzothiazole selectively binds to nickel ions through thiol groups, further stabilizing free metal ions. The three synergistically effectively reduce the ineffective deposition of nickel particles, extend the service life of the plating solution, and at the same time reduce the pinhole rate of the plating layer, thereby improving the surface density and uniformity.

[0044] The surfactant includes alkyl glycoside or sophorolipid, and the molar ratio of the surfactant to the citric acid is 1:10-1:20.

[0045] Specifically, the surfactant (alkyl glycoside or sophorolipid) reduces the surface tension of the plating solution, enhances the wetting and penetration ability, ensures the uniform spreading of the plating solution on the surface of complex substrates, and eliminates blind spots in the plating such as micropores and grooves. Its molar ratio with citric acid optimizes the synergistic effect between organic molecules, forms a dynamic micelle structure through hydrogen bonds or van der Waals forces, and further improves the directional transmission efficiency of nickel ions. The introduction of its bio-based surfactant not only reduces defects such as pinholes and air gaps in the plating, but also gives the system environmentally friendly properties.

[0046] A method for preparing a chemical nickel plating solution based on the synergistic effect of multiple complexing agents, the method comprising the following steps:

[0047] S1, dissolving nickel salt in deionized water to obtain a nickel salt solution;

[0048] S2. performing low-temperature plasma activation treatment on the multi-component complexing agent;

[0049] S3, first add a weak complexing agent to the nickel salt solution, stir for 10 to 30 minutes, and then add a strong complexing agent and nanoparticles in sequence;

[0050] S4, adding sodium hypophosphite, stabilizer and surfactant, and stirring and mixing;

[0051] S5. Adjust the pH to 4.5-5.5, and obtain a chemical nickel plating solution after two-stage filtration.

[0052] Specifically, S1 provides uniform and stable nickel ions (Ni2 + ) source, the high purity of deionized water avoids interference from impurity ions, ensures precise control of subsequent complexation reactions, lays the foundation for the stability of the plating solution system and the uniform deposition of the coating, and creates a clean chemical environment for the synergistic effect of multiple complexing agents.

[0053] S2 uses low-temperature plasma activation to treat multi-component complexing agents, and uses high-energy active particles (such as ions and free radicals) to bombard the surface of complexing agent molecules, which significantly enhances the chemical activity of their functional groups (such as carboxyl and amino groups), thereby improving the binding ability of the complexing agent with nickel ions, thereby reducing the amount of complexing agent used and inhibiting the ineffective hydrolysis or side reactions of nickel ions by optimizing the complexing stability, extending the service life of the plating solution, and promoting uniform densification of the coating and reducing pores and defects.

[0054] S3 achieves dynamic control of nickel ions and optimization of coating structure by step-by-step addition of weak complexing agents, strong complexing agents, and nanoparticles. That is, weak complexing agents preferentially form loose complexes with nickel ions, promoting the rapid formation and uniform distribution of initial nickel nuclei. Strong complexing agents are then added to enhance complex stability, inhibit excessive release of nickel ions, and prevent self-decomposition of the plating solution. Finally, nanoparticles are introduced as heterogeneous nucleation sites to refine grains and enhance coating density. Its gradient complexation strategy balances reaction rate and bath stability, while significantly improving coating hardness and corrosion resistance through co-deposition of nanoparticles.

[0055] S4 achieves synergistic optimization of the reduction reaction and the plating solution system by sequentially adding sodium hypophosphite, stabilizer, and surfactant and fully stirring and mixing. Sodium hypophosphite acts as a reducing agent to drive the chemical reduction deposition of nickel ions to form a nickel-phosphorus alloy coating. The stabilizer selectively inhibits spontaneous decomposition of the plating solution and interference from impurities to ensure the controllability of the reaction. The surfactant reduces surface tension, improves the wetting and permeability of the plating solution to complex substrates, and eliminates pores and local defects in the coating. The three work together to ensure a uniform, dense, and structurally stable coating, while maintaining the high efficiency of the plating solution and long-term operational reliability.

[0056] S5 optimizes the chemical environment of the plating solution and removes impurities by adjusting the pH of the plating solution to 4.5-5.5 and performing two-stage filtration. pH control ensures a balance between the stability of nickel ion complexation and the reducing activity of sodium hypophosphite, avoiding nickel salt hydrolysis precipitation or uncontrolled reaction rate. Two-stage filtration improves the purity of the plating solution and eliminates defects such as pinholes and roughness in the plating layer.

[0057] The power of the low-temperature plasma treatment in S2 is 80-100W, the treatment time is 2-4 minutes, and the plasma gas includes a mixture of argon and oxygen, with a volume ratio of argon to oxygen of 9:1.

[0058] Specifically, through low-temperature plasma treatment of a mixed gas of argon and oxygen, its high-energy active particles selectively activate the molecular surface of the multi-component complexing agent, significantly enhancing the chemical activity of its functional groups such as carboxyl and amino groups, while avoiding excessive etching to destroy the molecular structure. The argon-dominated bombardment cleans the surface of the complexing agent and introduces defect sites, while oxygen promotes the oxidative modification of functional groups, thereby optimizing the nickel ion adsorption and coordination ability of the complexing agent.

[0059] In S3, the interval between adding the weak complexing agent and the strong complexing agent is 15 to 25 minutes, the dissolution temperature of the weak complexing agent is 40-50°C, and the dissolution temperature of the strong complexing agent is 25-35°C.

[0060] Specifically, in S3, the dynamic release of nickel ions is optimized through step-by-step gradient complexation and temperature control. The higher dissolution temperature of the weak complexing agent accelerates its initial combination with nickel ions to form a loose complex to initiate the nucleation of the coating. The interval time ensures that the weak complexing agent can fully act, and then the strong complexing agent is introduced at a lower temperature. The strong coordination stabilizes the nickel ions, inhibits hydrolysis or non-selective deposition, balances the reaction rate and the stability of the plating solution, reduces the fluctuation of the free nickel ion concentration, thereby improving the uniformity of the coating, reducing the porosity, and extending the service life of the plating solution, realizing an efficient and controllable chemical deposition process.

[0061] The pH in S5 was adjusted using a gradient adjustment method. First, the pH was adjusted to 5.0-5.5 using citric acid, and then fine-tuned to 4.5-5.0 using ammonia water. The temperature was adjusted to 30-32°C.

[0062] Specifically, S5 uses a gradient adjustment method to control the pH in stages to avoid nickel ion complex imbalance or uncontrolled decomposition of sodium hypophosphite caused by drastic pH fluctuations. Citric acid, as a weak acid and complexing agent, preferentially neutralizes some alkaline components and enhances the stability of the nickel complex. Ammonia water fine-tuning lowers the pH and reduces interference from impurities introduced by excess acid.

[0063] The two-stage filtration in S5 includes: pre-filtration, using a filter element with a pore size of 1-5 μm to remove large particle agglomerates;

[0064] Nanofiltration uses a filter element with a pore size of 0.1-0.5 μm to retain undispersed nanoparticle aggregates.

[0065] Specifically, S5 pre-filtration removes large particle agglomerates (such as undissolved nickel salts or complexing agent aggregates) to prevent them from clogging subsequent filter elements or causing rough coatings. Nano-scale filtration accurately intercepts undispersed nanoparticle aggregates while retaining fully dispersed functional nanoparticles to ensure their effectiveness as heterogeneous nucleation sites. The two-stage filtration combination significantly improves the purity of the plating solution and the uniformity of nanoparticle dispersion, reducing the porosity and surface defects of the coating.

[0066] Example 1

[0067] Formula of chemical nickel plating solution: nickel salt (nickel sulfate): 25 parts, sodium hypophosphite: 30 parts, multi-component complexing agent: 38 parts, weak complexing agent (lactic acid): 12 parts, strong complexing agent (25 parts of citric acid + 1 part of EDTA), nanoparticles (carboxylated SiO2, particle size 50nm): 1.5 parts, stabilizer: 0.5 parts, thiourea: 0.3 parts, cerium chloride: 0.2 parts, surfactant (alkyl glycoside): 1.5 parts and ionized water: balance.

[0068] Preparation method:

[0069] S101: Dissolve 25 parts of nickel sulfate in deionized water, and stir magnetically (300 rpm, 45° C.) until completely dissolved.

[0070] S102: The multi-component complexing agent (lactic acid, citric acid, EDTA) was treated with low-temperature plasma (power 80 W, time 3 minutes, argon:oxygen=9:1).

[0071] S103: Lactic acid (12 parts, stirred at 45°C for 15 minutes) was added to the nickel salt solution, and citric acid + EDTA (25 + 1 parts, 30°C) was added after an interval of 20 minutes, followed by the addition of nano-SiO2 (1.5 parts) and ultrasonic dispersion (300W, 20 minutes).

[0072] S104: Sodium hypophosphite (30 parts), stabilizer (0.3 parts of thiourea + 0.2 parts of cerium chloride), and alkyl glycoside (1.5 parts) were added and mixed by microfluidics (channel inner diameter 0.5 mm, flow rate 30 mL / min).

[0073] S105: Adjust the pH to 5.2 with citric acid and slightly adjust the pH to 4.8 (30° C.) with ammonia water, and perform pre-filtration and nano-filtration.

[0074] Example 2

[0075] Chemical nickel plating solution formula: nickel salt (nickel chloride): 30 parts, sodium hypophosphite: 35 parts, multi-component complexing agent: 45 parts, weak complexing agent (malic acid): 10 parts, strong complexing agent (citric acid 30 parts + EDTA 3 parts), nanoparticles (amino carbon quantum dots, particle size 20nm): 2 parts, stabilizer: 0.8 parts, thiourea: 0.5 parts, lanthanum nitrate: 0.3 parts, surfactant (sophorolipid): 2 parts and ionized water: balance

[0076] Preparation method:

[0077] S201: Dissolve 30 parts of nickel chloride in deionized water, and stir magnetically (400 rpm, 50° C.) until completely dissolved.

[0078] S202: The multi-component complexing agent (malic acid, citric acid, EDTA) is treated with low-temperature plasma (power 100 W, time 4 minutes, argon:oxygen = 9:1).

[0079] S203: Malic acid (10 parts, stirred at 50°C for 10 minutes) was added to the nickel salt solution, and citric acid + EDTA (30 + 3 parts, 25°C) was added after an interval of 25 minutes, followed by the addition of carbon quantum dots (2 parts) and ultrasonic dispersion (400W, 30 minutes).

[0080] S204: Sodium hypophosphite (35 parts), stabilizer (0.5 parts of thiourea + 0.3 parts of lanthanum nitrate), and sophorolipid (2 parts) were added and mixed by microfluidics (channel inner diameter 0.8 mm, flow rate 40 mL / min).

[0081] S205: Adjust the pH to 5.5 with citric acid, slightly adjust the pH to 5.0 with ammonia (32°C), pre-filter (3 μm filter element), and nano-filter (0.3 μm ceramic filter element).

[0082] Table 1 is a performance comparison table of two embodiments

[0083] Example 1 Example 2 Self-decomposition time (hours) 12 14 Coating hardness (HV) 1100-1150 1200-1250 Nickel plating speed (μm / h) 18-20 20-22

[0084] In terms of self-decomposition time, the self-decomposition time of Example 1 is 12 hours, and the plating solution stability meets conventional industrial requirements. Nickel sulfate and cerium chloride stabilizers are used. The nickel sulfate system has mild chemical properties, and cerium chloride inhibits the non-selective reduction of nickel ions through colloidal hydroxide. However, the amount of rare earth salt used is low, which has limited inhibition on hydrogen evolution, resulting in slightly poorer stability.

[0085] In Example 2, the self-decomposition time is extended to 14 hours. Nickel chloride and lanthanum nitrate stabilizers are used. The lanthanum salt in the nickel chloride system forms a denser colloidal barrier in the plating solution. Combined with the high dispersion of carbon quantum dots, it effectively blocks the active sites of impurities, reduces the ineffective deposition of nickel ions, and suppresses side reactions more efficiently.

[0086] In terms of coating hardness: Example 1 mainly relies on the heterogeneous nucleation effect of carboxylated silica. Silica combines with nickel ions through surface carboxyl groups to refine the grains and form a nickel-phosphorus-silicon composite structure. However, due to the large particle size and limited surface activity, the grain refinement effect is relatively weak.

[0087] The strengthening effect of the amino-treated carbon quantum dots in Example 2, the smaller particle size of the carbon quantum dots and the high chemical activity of the amino functional groups provide more nucleation sites, further refining the grain size to the nanoscale. At the same time, the rigid skeleton of the carbon quantum dots is co-deposited with the nickel-phosphorus alloy to form a high-strength composite coating.

[0088] In terms of nickel plating speed: In Example 1, the amount of sodium hypophosphite used is related to the wettability of the surfactant. In the nickel sulfate system, the weak complexing agent preferentially releases nickel ions, but the wetting and permeability of the alkyl glycoside is weak, and the deposition efficiency in the microporous area is limited, resulting in a medium plating speed.

[0089] Example 2: The plating speed benefits from the synergistic effect of the sodium hypophosphite increment and the sophorolipid surfactant. The biocompatibility and low surface tension properties of sophorolipid significantly enhance the wetting and spreading ability of the plating solution on complex substrates, making the nickel ion reduction reaction more efficient. At the same time, the nickel chloride system has a stronger activation effect on the substrate, further accelerating the deposition process.

[0090] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A chemical nickel plating solution based on the synergistic effect of multiple complexing agents, characterized in that: The preparation method comprises the following raw materials in parts by weight: 20-35 parts of nickel salt, 25-40 parts of sodium hypophosphite, 30-48 parts of multi-component complexing agent, 0.1-5 parts of stabilizer, 0.5-3 parts of surfactant, and the balance of ionized water; The multi-component complexing agent includes an organic complexing agent and nanoparticles, the organic complexing agent includes a weak complexing agent and a strong complexing agent, and the nanoparticles include silicon dioxide or carbon quantum dots.

2. The chemical nickel plating solution based on the synergistic effect of multiple complexing agents according to claim 1, characterized in that: The particle size of the nanoparticles is 1-100 nanometers, and the surface is modified with carboxyl or amino functional groups.

3. The chemical nickel plating solution based on the synergistic effect of multiple complexing agents according to claim 1, characterized in that: The weak complexing agent includes lactic acid or malic acid, accounting for 10-15 parts, and the strong complexing agent includes citric acid or ethylenediaminetetraacetic acid, accounting for 20-30 parts; The nanoparticles include silicon dioxide or carbon quantum dots, accounting for 1-2 parts.

4. The chemical nickel plating solution based on the synergistic effect of multiple complexing agents according to claim 1, characterized in that: The stabilizer includes thiourea, rare earth salt and 2-mercaptobenzothiazole, the rare earth salt includes cerium salt, lanthanum salt or neodymium salt, and the rare earth salt accounts for 0.2-0.5 parts.

5. The chemical nickel plating solution based on the synergistic effect of multiple complexing agents according to claim 1, characterized in that: The surfactant includes an alkyl glycoside or a sophorolipid, and the molar ratio of the surfactant to citric acid is 1:10-1:

20.

6. A method for preparing a chemical nickel plating solution based on the synergistic effect of multiple complexing agents, characterized in that: A chemical nickel plating solution based on the synergistic effect of multiple complexing agents according to any one of claims 1 to 5, the method comprising the following steps: S1, dissolving nickel salt in deionized water to obtain a nickel salt solution; S2. performing low-temperature plasma activation treatment on the multi-component complexing agent; S3, first add a weak complexing agent to the nickel salt solution, stir for 10 to 30 minutes, and then add a strong complexing agent and nanoparticles in sequence; S4, adding sodium hypophosphite, stabilizer and surfactant, and stirring and mixing; S5. Adjust the pH to 4.5-5.5, and obtain a chemical nickel plating solution after two-stage filtration.

7. The method for preparing a chemical nickel plating solution based on the synergistic effect of multiple complexing agents according to claim 6, characterized in that: The power of the low-temperature plasma treatment in S2 is 80-100 W, the treatment time is 2-4 minutes, and the plasma gas includes a mixed gas of argon and oxygen, and the volume ratio of the argon and oxygen is 9:

1.

8. The method for preparing a chemical nickel plating solution based on the synergistic effect of multiple complexing agents according to claim 6, characterized in that: In the above S3, the interval between adding the weak complexing agent and the strong complexing agent is 15 to 25 minutes, the dissolution temperature of the weak complexing agent is 40-50°C, and the dissolution temperature of the strong complexing agent is 25-35°C.

9. The method for preparing a chemical nickel plating solution based on the synergistic effect of multiple complexing agents according to claim 6, characterized in that: The pH in S5 is adjusted by a gradient adjustment method, first adjusting the pH to 5.0-5.5 with citric acid, then fine-tuning it to 4.5-5.0 with ammonia water, and controlling the temperature at 30-32°C.

10. The method for preparing a chemical nickel plating solution based on the synergistic effect of multiple complexing agents according to claim 6, characterized in that: The two-stage filtration in S5 includes: pre-filtration, using a filter element with a pore size of 1-5 μm to remove large particle agglomerates; Nanofiltration uses a filter element with a pore size of 0.1-0.5 μm to retain undispersed nanoparticle aggregates.

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