Electroplating solution for palladium plating of silver substrate and preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of metal plating solutions and medical radioactive source cores, and particularly relates to an electroplating solution for plating palladium on a silver substrate as well as a preparation method and application of the electroplating solution. The electroplating solution comprises dichlorodiamminepalladium, ammonium chloride, diammonium hydrogen phosphate, polyethylene glycol and ammonia water, the pH is 7.5-9, interface corrosion to a silver substrate can be avoided in a neutral-weak alkaline environment, the stability of the electroplating solution can be remarkably improved through cooperation of all components in a system, and a compact palladium plating layer with low porosity is obtained. In addition, the utilization rate of palladium is high, waste liquid is easy to recover, the loss of precious metal is reduced, the economical efficiency and the environmental protection property of the process are improved, and the method is particularly suitable for the 90Sr applicator with strict requirements for the compactness and the irradiation resistance of a plating layer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal plating solution and medical radioactive source core preparation, in particular to a palladium plating solution for silver substrate, a preparation method and application thereof, and specifically to a palladium plating solution for silver substrate of applicator without etching and application thereof. BACKGROUND

[0002] In the manufacture and application of 90Sr applicator source core, high-purity silver sheet is used as a key matrix material for carrying radionuclides. However, the bare silver sheet has a risk of corrosion in a long-term use environment (such as contact with air humidity or potential body fluid), which may cause leaching of radionuclides and lead to safety and radioactive pollution hazards. To solve the corrosion leakage, a dense layer of metal palladium (Pd) must be electroplated on the surface of the silver sheet of the source core to provide a corrosion-resistant barrier by virtue of its excellent chemical inertness, thereby ensuring safe and reliable application of the 90Sr applicator.

[0003] The existing palladium plating solution in the existing palladium plating process has significant defects in actual application, whether it is a strong acid plating solution system or an amino sulfonic acid palladium system: high internal stress of the plating layer, easy corrosion of the silver substrate in a strong acid environment, and displacement reaction affecting the bonding force; although the amino sulfonic acid palladium system reduces corrosion, it has high cost and the plating layer is prone to cracking. The structure of the 90Sr applicator source core is a three-in-one rolled silver sheet with a silver substrate as the base material, and the innermost layer is a radionuclide layer. The silver substrate must not be corroded during the electroplating process to prevent leakage of radionuclides. The composition of the traditional palladium plating solution is not suitable for the silver substrate, and it is urgent to develop a suitable plating solution composition formula that not only meets the zero corrosion of the silver substrate but also optimizes the cost while ensuring the performance of the plating layer.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The present application aims to provide a palladium plating solution for silver substrate, which can be used for zero corrosion of silver substrate and has excellent performance of palladium plating layer and lower cost, and a preparation method thereof, and application thereof in palladium plating of silver substrate.

[0006] The present application provides a palladium plating solution for silver substrate, characterized in that the palladium plating solution comprises dichlorodiammine palladium, ammonium chloride, diammonium hydrogen phosphate, polyethylene glycol and ammonia water.

[0007] In some embodiments of the present application, the content of dichlorodiammine palladium in the plating solution is 10-25 g / L, the content of ammonium chloride is 50-80 g / L, the content of diammonium hydrogen phosphate is 50-80 g / L, and the content of polyethylene glycol is 10-500 mg / L.

[0008] In some embodiments of the present application, the content of the dichloro diammine palladium in the electroplating solution is 10-20 g / L, the content of the ammonium chloride is 60-80 g / L, the content of the diammonium hydrogen phosphate is 60-75 g / L, and the content of the polyethylene glycol is 10-50 mg / L.

[0009] In some embodiments of the present application, the ammonia water in the electroplating solution is used to dissolve the dichloro diammine palladium and / or adjust the pH value and / or ionic activity of the solution. Preferably, the content of the ammonia water in the electroplating solution is 5-15 ml / L, more preferably 8-12 ml / L, and the ammonia water is concentrated ammonia water.

[0010] In some specific embodiments of the present application, the electroplating solution comprises 10 g / L of the dichloro diammine palladium, 60 g / L of the ammonium chloride, 60 g / L of the diammonium hydrogen phosphate, 20 mg / L of the polyethylene glycol, and 10 ml / L of the ammonia water. The ammonia water is concentrated ammonia water.

[0011] In some specific embodiments of the present application, the electroplating solution comprises 25 g / L of the dichloro diammine palladium, 80 g / L of the ammonium chloride, 75 g / L of the diammonium hydrogen phosphate, 10 mg / L of the polyethylene glycol, and 10 ml / L of the ammonia water. The ammonia water is concentrated ammonia water.

[0012] In some embodiments of the present application, the electroplating solution further comprises hydrochloric acid. Preferably, the hydrochloric acid is 10% hydrochloric acid by mass fraction. The hydrochloric acid and the ammonia water in the electroplating solution are used to adjust the pH of the electroplating solution. The hydrochloric acid and the ammonia water also serve as ionic activity adjustors.

[0013] In some embodiments of the present application, the electroplating solution further comprises water. Preferably, the water is deionized water.

[0014] In some embodiments of the present application, the pH of the electroplating solution is 7.5-9.

[0015] The present application also provides a preparation method of the above-mentioned electroplating solution, which comprises the following steps: dissolving the dichloro diammine palladium in the ammonia water to obtain a solution C; adding the ammonium chloride, the diammonium hydrogen phosphate, and the polyethylene glycol into water to stir and dissolve, and adding the solution C to obtain a solution D; adjusting the pH value of the solution D to 7.5-9 to obtain the electroplating solution.

[0016] In some embodiments of the present application, the pH value of the solution D is adjusted to 7.5-9 by using a hydrochloric acid solution. If necessary, an appropriate amount of ammonia water can be added to adjust the pH value.

[0017] In some embodiments of the present application, the preparation method further comprises the following steps of preparing dichloro diammonium palladium: S1: adding palladium chloride into a hydrochloric acid solution, continuously stirring and dissolving to obtain a solution A; S2: adding ammonia water into the solution A dropwise, continuously stirring and mixing uniformly, then adding a hydrochloric acid solution, and the obtained precipitate B is dichloro diammonium palladium.

[0018] In some embodiments of the present application, the mass fraction of the hydrochloric acid solution is 5-20%, preferably 10%. In some embodiments of the present application, the temperature of the hydrochloric acid solution is 50-70℃, preferably 60℃.

[0019] In some embodiments of the present application, 10-20g of palladium chloride is added into 15-40ml of a 10% hydrochloric acid solution in step S1, and continuously stirred and dissolved to obtain a solution A. Preferably, the amount of the palladium chloride is 10g. Preferably, the amount of the 10% hydrochloric acid solution is 20ml.

[0020] In some embodiments of the present application, the amount of the ammonia water in step S2 is 40-70ml. Preferably, the amount of the ammonia water is 50ml. The ammonia water is concentrated ammonia water.

[0021] In some embodiments of the present application, the amount of the hydrochloric acid solution added in step S2 is 40-70ml of a 10% hydrochloric acid solution, which can be equal in volume to the concentrated ammonia water in step S2. Preferably, the amount of the hydrochloric acid solution is 50ml of a 10% hydrochloric acid solution.

[0022] In some embodiments of the present application, the temperature of the solution is maintained at 50-70℃, preferably 60℃, during the process of adding the ammonia water dropwise.

[0023] The present application further provides the use of the above-mentioned electroplating solution or the electroplating solution obtained by the above-mentioned preparation method in the palladium plating of a silver substrate.

[0024] The present application further provides a method for palladium plating of a silver substrate, which comprises the following steps: pretreating the silver substrate; adding the above-mentioned electroplating solution or the electroplating solution obtained by the above-mentioned preparation method into an electrolytic cell; placing the pretreated silver substrate into the electrolytic cell, and performing electroplating with a palladium sheet as an anode.

[0025] In some embodiments of the present application, the pretreatment comprises sequentially performing alkali washing, water washing, acid washing, water washing and drying. In some embodiments of the present application, the alkali washing solution comprises 10 g / L sodium hydroxide, 20 g / L sodium carbonate, 20 g / L sodium phosphate. Preferably, the alkali washing process comprises: immersing the silver substrate in the alkali washing solution and ultrasonic treatment for 10-15 min.

[0026] In some embodiments of the present application, the acid washing solution is 10% hydrochloric acid. Preferably, the acid washing process comprises: immersing the silver substrate in the acid washing solution and ultrasonic treatment for 10-15 min.

[0027] In some embodiments of the present application, the temperature of the electroplating solution is 20-30°C. In some embodiments of the present application, the current of the electroplating is direct current, preferably stepwise direct current.

[0028] In some embodiments of the present application, the method further comprises the steps of cleaning and drying after the electroplating is completed. For example, rinsing with water and wiping dry with a dust-free cloth after the electroplating is completed.

[0029] In some specific embodiments of the present application, the method for plating palladium on a silver substrate specifically comprises the following steps: (1) sequentially performing alkali washing, water washing, acid washing, water washing and drying on a 90Sr applicator silver substrate to obtain a pretreated substrate; (2) converting palladium chloride into palladium dichloride diamine powder, water washing and drying for standby use; (3) dissolving the palladium dichloride diamine powder in ammonia water, adding ammonium chloride, diammonium hydrogen phosphate and polyethylene glycol into deionized water, stirring until completely dissolved, adjusting the pH to 7.5-9 with 10% hydrochloric acid to obtain an electroplating solution; (4) placing the pretreated substrate into an electrolytic cell for electroplating, the current is stepwise direct current, the temperature of the plating solution is 20-30°C, and the anode is a palladium sheet; (5) rinsing with water and wiping dry with a dust-free cloth after the electroplating is completed.

[0030] The alkali washing solution is 10 g / L sodium hydroxide, 20 g / L sodium carbonate, 20 g / L sodium phosphate. The alkali washing process specifically comprises: immersing the 90Sr applicator silver substrate in the alkali washing solution and placing it together with the container into an ultrasonic cleaning machine for ultrasonic treatment for 10-15 min.

[0031] The acid washing solution is 10% hydrochloric acid. The acid washing process specifically comprises: immersing the 90Sr applicator silver substrate in the acid washing solution and placing it together with the container into an ultrasonic cleaning machine for ultrasonic treatment for 10-15 min.

[0032] Compared with the prior art, the present application has at least the following advantages: The electroplating solution provided by the present application uses dichlorodiammine palladium converted from palladium chloride as the palladium source, and the ammonia coordination structure thereof can not only inhibit the hydrolysis of palladium ions, but also effectively inhibit the hydrogen evolution side reaction. Meanwhile, the neutral-weak alkaline environment provided by the present application can avoid the interfacial corrosion of the silver substrate, in addition, the stability of the electroplating solution can be significantly improved through the cooperation of various components in the system, and a dense and low-porosity palladium plating layer can be obtained.

[0033] The electroplating solution provided by the present application is stable, and no discoloration and precipitation occurs within 180 days, the replacement frequency is lower than that of the traditional palladium plating solution, and the palladium ions in the deteriorated electroplating solution can be easily recovered as dichlorodiammine palladium (recovery rate ≥ 96%) through acidification, which can be recycled, thereby reducing the loss of noble metals and optimizing the cost.

[0034] The electroplating solution formula for non-etching palladium plating of the silver substrate provided by the present application converts palladium chloride into dichlorodiammine palladium as the palladium source of the electroplating solution, thereby avoiding the problem of easy hydrolysis and precipitation when palladium chloride is directly used, and the mild weak alkaline environment thereof reduces the corrosion risk of the silver substrate. This formula makes the release of palladium ions more uniform during the electroplating process, and in combination with the ammonia water-ammonium chloride buffer system, it can effectively inhibit the hydrogen evolution side reaction, thereby obtaining a dense palladium layer. In addition, the utilization rate of palladium is high, and the waste liquid is easy to recover, thereby reducing the loss of noble metals and improving the economic efficiency and environmental friendliness of the process, and it is particularly suitable for 90Sr applicators with strict requirements for the density and radiation resistance of the plating layer. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present disclosure or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art without creative labor.

[0036] Figure 1 The photo of the palladium-plated silver substrate obtained in Example 1. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0038] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. Unless otherwise stated, all percentages and ratios used herein are on a mass basis.

[0039] It should also be understood that the steps of the methods recited in the present application need not be performed in the recited order, unless otherwise stated, and that one or more of the steps of the methods can be performed simultaneously or omitted, unless otherwise stated. Moreover, the numbering of the steps of the methods is merely a convenient device to identify individual steps of the methods and is not meant to, nor should it be construed to, limit the relative ordering of the steps of the methods or the scope of the application. Changes in the relative ordering of the steps of the methods, or adjustments in the numbering of the steps of the methods, can be made without departing from the scope of the application, provided that the technical content of the method steps is not materially affected.

[0040] The technical solutions of the present application will be described clearly and completely below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative work are within the scope of protection of the present application.

[0041] Unless otherwise stated, all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further purification, and the instruments used in the examples are commercially available.

[0042] Example 1 The composition of the plating solution and the plating conditions of the present example are as follows: Dichlorodiammine palladium 10 g / L Ammonium chloride 60 g / L Diammonium hydrogen phosphate 60 g / L Polyethylene glycol 20 mg / L Ammonia 10 mL pH 7.5-9 Anode palladium sheet Current density 5 mA / cm 2 Time 60 min (1) Preparation of the plating solution The preparation method of the plating solution of the present example is as follows: 1. Slowly add 10 g of palladium chloride into 20 mL of 10% hydrochloric acid solution with temperature of 60±10℃, continuously stir to obtain solution A, which is brownish red.

[0043] 2. Keep the temperature of the brownish red solution A unchanged, drop 50 mL of ammonia water, continuously stir, cool, add 50 mL of 10% hydrochloric acid solution with temperature of 60±10℃ to obtain precipitate B.

[0044] 3. Dissolve precipitate B in 10 mL of ammonia water to obtain solution C.

[0045] 4. Add formula amount of ammonium chloride, polyethylene glycol and diammonium hydrogen phosphate into a container containing 100 mL of deionized water, stir, dissolve, then add solution C to obtain solution D.

[0046] 5. Add appropriate amount of hydrochloric acid solution to solution D to make its pH value range from 7.50 to 9.00, supplement deionized water to make the total volume of the solution 1000 mL to obtain a plating solution.

[0047] (2) Palladium plating on silver substrate The silver substrate of 90Sr applicator is pretreated: sequentially perform alkaline washing, water washing, acid washing, water washing and drying.

[0048] The alkaline washing treatment is specifically as follows: immerse the silver substrate of 90Sr applicator in an alkaline washing solution (10 g / L sodium hydroxide, 20 g / L sodium carbonate, 20 g / L sodium phosphate) and put it into an ultrasonic cleaning machine together with the container for ultrasonic treatment for 10-15 min.

[0049] The acid washing treatment is specifically as follows: immerse the silver substrate of 90Sr applicator in an acid washing solution and put it into an ultrasonic cleaning machine together with the container for ultrasonic treatment for 10-15 min.

[0050] Add the prepared plating solution into an electrolytic cell, keep the temperature of the plating solution at 20-30℃, put the above pretreated applicator silver substrate into the electrolytic cell, use palladium sheet as anode, and use 5 mA / cm 2 of direct current to electroplate for 60 min, and perform low-speed stirring during the electroplating process. After the electroplating is completed, rinse the applicator silver substrate with water and wipe it dry with a dust-free cloth. The obtained palladium plated silver substrate is shown in FIG. 2. Figure 1

[0051] Example 2 According to the following plating solution composition and plating conditions, prepare the plating solution by referring to the method of Example 1, and plate palladium on the silver substrate of 90Sr applicator.

[0052] Dichlorodiammine palladium 25 g / L Ammonium chloride 80 g / L ​Diammonium hydrogen phosphate 75 g / L Polyethylene glycol 10 mg / L Ammonia water 10 mL pH 7.5-9 Anode palladium sheet Current density 5 mA / cm 2 Time 60 min Experimental example The appearance and performance of the palladium plating layer of the applicator silver substrate obtained from the plating solutions of Example 1 and Example 2 were detected. The stability of the plating solution was detected according to the method of ISO 3696:1987, and the adhesion of the plating layer was detected according to the method of GB / T5270-2005. The detection results are shown in Table 1.

[0053] Table 1. Performance of the plating solution and plating layer of Example 1 and 2

[0054] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electroplating solution for palladium plating of silver substrates, characterized in that, The electroplating solution comprises dichloro diammine palladium, ammonium chloride, diammonium hydrogen phosphate, polyethylene glycol and ammonia water.

2. The electroplating solution of claim 1, wherein In the electroplating solution, the content of dichloro diammine palladium is 10-25 g / L, the content of ammonium chloride is 50-80 g / L, the content of diammonium hydrogen phosphate is 50-80 g / L, and the content of polyethylene glycol is 10-500 mg / L.

3. The electroplating solution of claim 1, wherein In the electroplating solution, the content of dichloro diammine palladium is 10-20 g / L, the content of ammonium chloride is 60-80 g / L, the content of diammonium hydrogen phosphate is 60-75 g / L, and the content of polyethylene glycol is 10-50 mg / L.

4. The electroplating solution of claim 1, wherein The pH of the electroplating solution is 7.5-9.

5. The method for preparing an electroplating solution according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: The dichloro diammine palladium is dissolved in ammonia water to obtain solution C; The ammonium chloride, the diammonium hydrogen phosphate and the polyethylene glycol are added into water and stirred to dissolve, and the solution C is added to obtain solution D; The pH of the solution D is adjusted to 7.5-9 to obtain the electroplating solution.

6. The production method according to claim 5, wherein The preparation method further comprises the following steps for preparing dichloro diammine palladium: S1: PdCl2 is added into hydrochloric acid solution, and continuous stirring is performed to dissolve to obtain solution A; S2: After ammonia water is added dropwise into the solution A and continuously stirred to be uniform, hydrochloric acid solution is added, and the obtained precipitate is dichloro diammine palladium.

7. The production method according to claim 6, characterized by, The mass fraction of the hydrochloric acid solution is 5-20%, and the temperature of the hydrochloric acid solution is 50-70℃.

8. The electroplating solution according to any one of claims 1-4 or the electroplating solution obtained by the preparation method according to any one of claims 5-7 is applied to silver substrate palladium plating.

9. A method of palladium plating a silver substrate, characterized by, The method comprises the following steps: The silver substrate is pretreated; The electroplating solution according to any one of claims 1-4 or the electroplating solution obtained by the preparation method according to any one of claims 5-7 is added into an electrolytic cell; The pretreated silver substrate is placed in the electrolytic cell, and palladium sheet is used as an anode for electroplating.

10. The method of claim 9, wherein, The temperature of the electroplating solution is 20-30℃, and the current of the electroplating is direct current.

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