A method for preparing electroless nickel-plated ceramic powder

Abstract

This invention discloses a method for preparing electroless nickel-plated ceramic powder. The method includes: pouring sensitized and activated ceramic powder into an electroless plating solution, mechanically stirring for 10-30 seconds and then stopping the stirring to allow the ceramic powder to settle to the bottom; restarting the mechanical stirring when bubbles emerge from the surface of the electroless plating solution; and filtering and sieving the mixture after the reaction is complete to obtain nickel-plated ceramic powder. This invention catalyzes the electroless plating reaction by controlling the stirring method during the electroless plating process, effectively reducing the plating time and increasing the plating rate of the powder. It alleviates the technical problems of incomplete and uneven coating of traditional electroless plated ceramic powder, resulting in ceramic powder with complete coating and significantly improved flowability.

Description

Technical Field

[0001] This invention belongs to the field of powder surface modification technology, and specifically relates to a method for preparing chemically nickel-plated ceramic powder. Background Technology

[0002] Ceramic powders such as diamond (C), silicon carbide (SiC), boron nitride (BN), and alumina (Al2O3) possess excellent physicochemical properties, including high strength, high hardness, low coefficient of linear expansion, and high wear resistance. They are often added as reinforcing phases to metal powders and are widely used in wear-resistant coatings where high friction and wear resistance is required. However, due to the covalent bonds inherent in ceramic powders, they lack good wettability with matrix materials such as metals, resulting in consistently low bonding strength between ceramics and metals. During wear and cutting processes, ceramic powders are prone to detaching from the metal matrix, leading to the failure of the original material.

[0003] To enhance the bonding strength between ceramic powder and metal, enabling composite materials to possess both the toughness of metal and the wear resistance of ceramic, the physicochemical properties of the ceramic surface are generally improved by synthesizing a metal layer on the ceramic surface. Common methods include electroless powder plating, powder alloying, electrochemical deposition, and vapor deposition. Compared to other methods, electroless powder plating utilizes a redox reaction to reduce metal ions to elemental metals and deposit them onto the substrate surface. Leveraging the catalytic activity of the deposited metal, the reaction can proceed continuously. This method requires no electrical energy and has attracted widespread attention as a low-cost and readily available preparation process.

[0004] Compared to bulk metals, the main challenges of electroless plating of ceramic powders are: 1. Since the ceramic surface lacks catalytic activity, additional active groups need to be introduced to give the ceramic powder surface catalytic activity; 2. The huge specific surface area of ​​the powder makes the electroless plating process time-consuming and extremely unstable, and the finer the powder particle size, the greater the difficulty of electroless plating. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a method for preparing electroless nickel-coated ceramic powder. This method effectively shortens the electroless plating time and significantly improves production efficiency. Furthermore, the electroless plated ceramic powder exhibits high nickel coating rate, good fluidity, and no issues such as incomplete plating or uneven plating. The compatibility between the ceramic powder and the metal is also significantly improved.

[0006] The specific details of the invention are as follows:

[0007] In a first aspect, the present invention provides a method for preparing electroless nickel-plated ceramic powder, the method comprising: pouring the sensitized and activated ceramic powder into an electroless plating solution, mechanically stirring for 10-30 seconds and then stopping the stirring to allow the ceramic powder to settle to the bottom;

[0008] When bubbles emerge from the surface of the chemical plating solution, restart the mechanical stirring; after the reaction is complete, perform post-processing on the mixture to obtain nickel-coated ceramic powder.

[0009] Optionally, the ceramic powder is cBN powder, and the particle size of the ceramic powder is 10-60 μm.

[0010] Optionally, the mechanical stirring speed is 90-180 r / min, which can make the ceramic powder uniformly suspended in the chemical plating solution.

[0011] Optionally, the sensitization and activation treatment includes: adding the roughened ceramic powder to the sensitization and activation solution and stirring for 30-60 minutes, then filtering and drying to obtain the sensitized and activated ceramic powder;

[0012] The sensitizing and activating solution is composed of a mixture of component A and component B.

[0013] Component A consists of sodium stannate, stannous chloride and concentrated hydrochloric acid; the mass-volume ratio of sodium stannate, stannous chloride and concentrated hydrochloric acid is 5-10:60-90:50-150.

[0014] Component B consists of palladium chloride, stannous chloride, and concentrated hydrochloric acid; the mass-to-volume ratio of palladium chloride, stannous chloride, and concentrated hydrochloric acid is 0.5-2.5:1-5:150-250.

[0015] Optionally, the preparation method of the sensitizing activation solution includes:

[0016] In step S11, stannous chloride is added to concentrated hydrochloric acid and stirred until completely dissolved. Then sodium stannate is added and stirred evenly to obtain component A.

[0017] S12. Add palladium chloride to concentrated hydrochloric acid and stir until completely dissolved. Then add an appropriate amount of distilled water, then add stannous chloride and stir until homogeneous to obtain component B.

[0018] S13. Slowly pour component A into component B, and keep the mixed solution at a constant temperature of 30-50℃ for 3-10 hours to obtain the sensitized activation solution.

[0019] Optionally, the roughening treatment includes: adding the ceramic powder to a roughening liquid and performing a roughening treatment to obtain the roughened ceramic powder;

[0020] The roughening solution is a mixed solution composed of hydrofluoric acid, ammonium fluoride and deionized water; the amount of hydrofluoric acid used is 15-35 ml / L, and the amount of ammonium fluoride used is 1-4 g / L.

[0021] Optionally, the electroless plating solution includes: nickel sulfate, sodium hypophosphite, lactic acid, propionic acid, sodium dodecyl sulfate, and thiourea;

[0022] The mass ratio of nickel sulfate, sodium hypophosphite, lactic acid, propionic acid, sodium dodecyl sulfate, and thiourea is 27-34:16-24:16-24:6-10:(6-10)*10. -3 :(2-4)*10 -3 .

[0023] Optionally, the initial pH of the electroless plating solution before formal electroless plating is 5.8-6.4.

[0024] Optionally, the post-processing includes filtering, washing, and drying the mixture.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] This invention provides a method for preparing electroless nickel-plated ceramic powder. This method accelerates the occurrence of the catalytic electroless nickel plating reaction by improving the stirring method in the electroless plating process, so that the electroless plating reaction proceeds rapidly and the ceramic powder is fully coated. This effectively improves the surface wettability of the ceramic powder, increases the bonding strength between it and the metal, and enhances the flowability of the ceramic powder. The process is simple and the process quality is stable. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The SEM image of the electroless nickel-plated cBN ceramic powder provided in the embodiment of the present invention is shown. Detailed Implementation

[0029] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0030] Specific experimental steps or conditions are not specified in the examples; however, they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products.

[0031] The present invention aims to provide a method for preparing electroless nickel-plated ceramic powder, the method comprising: pouring sensitized and activated ceramic powder into an electroless plating solution, mechanically stirring for 10-30 seconds and then stopping the stirring to allow the ceramic powder to settle to the bottom; restarting the mechanical stirring when bubbles emerge from the surface of the electroless plating solution; and after the reaction is completed (approximately 20-30 minutes later), performing post-treatment on the mixture to obtain nickel-plated ceramic powder.

[0032] In practical implementation, in existing technologies, after ceramic powder is poured into the electroless plating solution, it generally requires continuous stirring for 20-40 minutes before the electroless plating reaction begins. However, this invention stops stirring for a period of time (1-2 minutes) initially, allowing the ceramic powder to settle in the container. Because the surface of the ceramic powder contains colloidal palladium with catalytic activity, the accumulated colloidal palladium rapidly catalyzes the electroless plating reaction. Then, mechanical stirring is resumed until the reaction is complete, which takes only 20-30 minutes, completing the nickel coating process. Using the stirring method provided by this invention, the electroless plating reaction can be catalyzed within 1-2 minutes after the ceramic powder is poured into the electroless plating solution, greatly reducing unnecessary time in the electroless plating process and effectively improving production efficiency. Furthermore, the coated ceramic powder has a high coating rate, good fluidity, and no issues such as missed plating or uneven plating occur, significantly improving the compatibility between the ceramic powder and the metal.

[0033] In some embodiments, the ceramic powder is cBN powder with a particle size of 10-60 μm.

[0034] In some embodiments, the mechanical stirring rate is 90-180 r / min, which enables the ceramic powder to be uniformly suspended in the chemical plating solution.

[0035] In some embodiments, the sensitization and activation treatment includes: adding the roughened ceramic powder to the sensitization and activation solution and stirring for 30-60 minutes, then filtering and drying to obtain the sensitized and activated ceramic powder;

[0036] The sensitizing and activating solution is composed of a mixture of component A and component B. Component A consists of sodium stannate, stannous chloride, and concentrated hydrochloric acid, with a mass-to-volume ratio of 5-10:60-90:50-150. Component B consists of palladium chloride, stannous chloride, and concentrated hydrochloric acid, with a mass-to-volume ratio of 0.5-2.5:1-5:150-250.

[0037] As a preferred outcome, in component A, the mass-volume ratio of sodium stannate, stannous chloride, and concentrated hydrochloric acid is 6-9:70-80:80-120, or it can be 7-8:70-75:90-110; in component B, the mass-volume ratio of palladium chloride, stannous chloride, and concentrated hydrochloric acid is 1-2:2-4:180-220, or it can be 1-1.2:2-3:190-210.

[0038] In some embodiments, the method for preparing the sensitizing activation solution includes:

[0039] S11. Add stannous chloride to concentrated hydrochloric acid and stir until completely dissolved. Then add sodium stannate and stir until homogeneous to obtain component A.

[0040] S12. Add palladium chloride to concentrated hydrochloric acid and stir until completely dissolved. Then add an appropriate amount of distilled water, then add stannous chloride and stir until homogeneous to obtain component B.

[0041] S13. Slowly pour component A into component B, and keep the mixed solution at a constant temperature of 30-50℃ for 3-10 hours to obtain the sensitization and activation solution.

[0042] In specific implementation, the present invention configures the reaction raw materials of the sensitization and activation solution in groups. Component A mainly contains stannous chloride and stannate ions; while in component B, under the condition of concentrated hydrochloric acid as solvent and providing an acidic reaction environment, palladium chloride undergoes a disproportionation reaction with a certain amount of stannous chloride to form palladium particles, namely, SnCl2 + PdCl2 → SnCl4 + Pd (colloid); then component A is slowly poured into component B, and sufficient stannous chloride is added after thorough mixing. The mixed solution forms a stable colloidal palladium solution during the static heat preservation process.

[0043] This invention effectively avoids the formation of a non-catalytically active, grass-green complex by adding stannous chloride in stages to react with palladium chloride in an acidic solution. This reduces the loss of palladium chloride and greatly improves the activity and stability of the prepared colloidal palladium-activated solution.

[0044] In some embodiments, the roughening process includes: adding ceramic powder to a roughening liquid and performing a roughening process to obtain roughened ceramic powder;

[0045] The roughening solution is a mixed solution composed of hydrofluoric acid, ammonium fluoride and deionized water; the amount of hydrofluoric acid used is 15-35 ml / L, and the amount of ammonium fluoride used is 1-4 g / L.

[0046] In some embodiments, the electroless plating solution includes: nickel sulfate, sodium hypophosphite, lactic acid, propionic acid, sodium dodecyl sulfate, and thiourea;

[0047] The mass ratio of nickel sulfate, sodium hypophosphite, lactic acid, propionic acid, sodium dodecyl sulfate, and thiourea is 27-34:16-24:16-24:6-10:(6-10)*10. -3 :(2-4)*10 -3 The dosage of sodium dodecyl sulfate and thiourea is measured in mg / L, which is one-thousandth of the dosage of the aforementioned chemicals. For example, the dosage of nickel sulfate can be 27 g / L, sodium hypophosphite 16 g / L, lactic acid 16 g / L, propionic acid 6 g / L, sodium dodecyl sulfate 6 mg / L, and thiourea 2 mg / L.

[0048] In some implementations, the initial pH of the electroless plating solution is 5.8-6.4 before the formal electroless plating.

[0049] In some embodiments, post-processing includes filtering, washing, and drying the mixture.

[0050] To enable those skilled in the art to better understand this application, the following embodiments will be used to provide a detailed description of a method for preparing electroless nickel-plated ceramic powder.

[0051] Example 1

[0052] cBN ceramic powder with an average particle size of 15-35μm was selected, poured into a roughening solution (15ml / L of hydrofluoric acid, 1g / L of ammonium fluoride, and the remainder of deionized water), and subjected to ultrasonic vibration for 30min of surface roughening. Then it was filtered and dried at 70℃ for 1h.

[0053] Preparation of sensitization and activation solution:

[0054] Preparation of component A solution: Pour 60g of stannous chloride into 70ml of concentrated hydrochloric acid and stir constantly until completely dissolved. Then add 6g of sodium stannate and stir well.

[0055] Preparation of component B solution: Add 0.8g palladium chloride to 160ml concentrated hydrochloric acid and stir until completely dissolved. Then add 100ml distilled water, followed by 2g stannous chloride, and stir continuously for 8 minutes to allow the stannous chloride and palladium chloride to react fully.

[0056] Component A was then dissolved and slowly poured into the solution of component B. Finally, the prepared colloidal palladium solution was placed in an aqueous solution at 35°C for 3 hours to obtain the sensitization and activation solution.

[0057] The coarsened cBN powder was poured into the sensitization and activation solution and stirred for 30 minutes, then filtered and dried at 50°C.

[0058] The surface-sensitized and activated cBN ceramic powder was poured into a chemical plating solution (containing 27 g / L nickel sulfate, 16 g / L sodium hypophosphite, 16 g / L lactic acid, 6 g / L propionic acid, 6 mg / L sodium dodecyl sulfate, and 2 mg / L thiourea; pH = 6, 65℃). The solution was stirred at 90 rpm while pouring the cBN powder. After all the cBN powder was added, stirring continued for 10 seconds to ensure uniform distribution. Stirring was then stopped to allow cBN deposition. When bubbles began to appear on the surface of the solution (this process takes approximately 30-60 seconds), stirring was resumed until no more bubbles appeared, indicating the end of the chemical plating process. Finally, the plating solution was filtered and dried at 70℃ to obtain electroless nickel-plated cBN ceramic powder.

[0059] Example 2

[0060] cBN ceramic powder with an average particle size of 15-35μm was selected, poured into a roughening solution (20ml / L of hydrofluoric acid, 2g / L of ammonium fluoride, and the remainder of deionized water), and subjected to ultrasonic vibration for 60min of surface roughening. Then it was filtered and dried at 70℃ for 1h.

[0061] Preparation of sensitization and activation solution:

[0062] Preparation of component A solution: Pour 90g of stannous chloride into 120ml of concentrated hydrochloric acid and stir continuously until completely dissolved. Then add 9g of sodium stannate and stir well.

[0063] Preparation of component B solution: Add 2.5g palladium chloride to 250ml concentrated hydrochloric acid and stir until completely dissolved. Then add 100ml distilled water, followed by 5g stannous chloride, and stir continuously for 12min to allow the stannous chloride and palladium chloride to react fully.

[0064] Component A was then dissolved and slowly poured into the solution of component B. Finally, the prepared colloidal palladium solution was placed in an aqueous solution at 45°C for 5 hours to obtain a highly efficient sensitizing and activating solution.

[0065] The coarsened cBN powder was poured into the sensitization and activation solution and stirred for 30 minutes, then filtered and dried at 50°C.

[0066] The surface-sensitized and activated cBN ceramic powder was poured into a chemical plating solution (containing 30 g / L nickel sulfate, 19 g / L sodium hypophosphite, 18 g / L lactic acid, 7 g / L propionic acid, 7 mg / L sodium dodecyl sulfate, and 3 mg / L thiourea; pH = 6, 70℃). The solution was stirred at 120 rpm while pouring the cBN powder. After all the cBN powder was added, stirring continued for 20 seconds to ensure uniform distribution. Stirring was then stopped to allow cBN deposition. When bubbles began to appear on the surface of the solution (this process takes approximately 30-60 seconds), stirring was resumed until no more bubbles appeared, indicating the end of the chemical plating process. Finally, the plating solution was filtered and dried at 70℃ to obtain electroless nickel-plated cBN ceramic powder.

[0067] Example 3

[0068] cBN ceramic powder with an average particle size of 15-35μm was selected, poured into a roughening solution (hydrofluoric acid 30ml / L, ammonium fluoride 3g / L, and the remainder deionized water), and subjected to ultrasonic vibration for surface roughening for 30min. Then it was filtered and dried at 70℃ for 1h.

[0069] Preparation of sensitization and activation solution:

[0070] Preparation of component A solution: Pour 75g of stannous chloride into 100ml of concentrated hydrochloric acid and stir continuously until completely dissolved. Then add 8g of sodium stannate and stir well.

[0071] Preparation of component B solution: Add 1.2g palladium chloride to 200ml concentrated hydrochloric acid and stir until completely dissolved. Then add 100ml distilled water, followed by 2.6g stannous chloride, and stir continuously for 10 minutes to ensure complete reaction between stannous chloride and palladium chloride. Then slowly pour the dissolved component A solution into the component B solution. Finally, place the prepared colloidal palladium solution in an aqueous solution at 40℃ for 4 hours to obtain the highly efficient sensitizing and activating solution.

[0072] The coarsened cBN powder was poured into the sensitization and activation solution and stirred for 30 minutes, then filtered and dried at 50°C.

[0073] The surface-sensitized and activated cBN ceramic powder was poured into a chemical plating solution (containing 33 g / L nickel sulfate, 21 g / L sodium hypophosphite, 20 g / L lactic acid, 8 g / L propionic acid, 8 mg / L sodium dodecyl sulfate, and 3 mg / L thiourea; pH 6.4, 75℃). The solution was stirred at 180 rpm while pouring the cBN powder. After all the cBN powder was added, stirring continued for 30 seconds to ensure uniform distribution. Stirring was then stopped to allow cBN deposition. When bubbles began to appear on the surface of the solution (approximately 30-60 seconds), stirring was resumed until no more bubbles appeared, indicating the end of the chemical plating process. Finally, the plating solution was filtered and dried at 70℃ to obtain electroless nickel-plated cBN ceramic powder.

[0074] Figure 1 The following is a SEM image of cBN ceramic powder after surface sensitization and activation using the sensitization and activation solution provided in the embodiments of the present invention, as shown. Figure 1 As shown, the nickel coating on the surface of the cBN ceramic powder is intact, with no instances of incomplete plating or uneven plating.

[0075] The preparation method of electroless nickel-plated ceramic powder provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing electroless nickel-plated ceramic powder, characterized in that, The method includes: The roughened ceramic powder is added to the sensitization and activation solution and stirred for 30-60 minutes, then filtered and dried to obtain the sensitized and activated ceramic powder. The sensitized and activated ceramic powder is poured into the chemical plating solution, mechanically stirred for 10-30 seconds, and then the stirring is stopped to allow the ceramic powder to settle to the bottom. When bubbles emerge from the surface of the electroless plating solution, mechanical stirring is restarted until the reaction is complete; subsequently, the mixture is post-treated to obtain nickel-coated ceramic powder. The ceramic powder is cBN powder, and the particle size of the ceramic powder is 10-60µm; The electroless plating solution comprises: nickel sulfate, sodium hypophosphite, lactic acid, propionic acid, sodium dodecyl sulfate, and thiourea; the initial pH of the electroless plating solution before formal electroless plating is 5.8-6.

4. The sensitizing and activating solution is composed of a mixture of component A and component B. Component A consists of sodium stannate, stannous chloride and concentrated hydrochloric acid; the mass-volume ratio of sodium stannate, stannous chloride and concentrated hydrochloric acid is 5-10:60-90:50-150. Component B is composed of palladium chloride, stannous chloride, and concentrated hydrochloric acid; the mass-to-volume ratio of palladium chloride, stannous chloride, and concentrated hydrochloric acid is 0.5-2.5:1-5:150-250. Component A is slowly poured into component B, and the mixed solution is kept at a constant temperature of 30-50℃ for 3-10 hours to obtain the sensitized activation solution.

2. The preparation method according to claim 1, characterized in that, The mechanical stirring speed is 90-180 r / min, which can make the powder uniformly suspended in the chemical plating solution.

3. The preparation method according to claim 1, characterized in that, The preparation methods for the sensitization and activation solution include: S11. Add stannous chloride to concentrated hydrochloric acid and stir until completely dissolved. Then add sodium stannate and stir until homogeneous to obtain component A. S12. Add palladium chloride to concentrated hydrochloric acid and stir until completely dissolved. Then add an appropriate amount of distilled water, followed by stannous chloride. Stir until homogeneous to obtain component B.

4. The preparation method according to claim 1, characterized in that, The roughening process includes: adding the ceramic powder to a roughening liquid and performing a roughening process to obtain the roughened ceramic powder; The roughening solution is a mixed solution composed of hydrofluoric acid, ammonium fluoride and deionized water; the amount of hydrofluoric acid used is 15-35 ml / L, and the amount of ammonium fluoride used is 1-4 g / L.

5. The preparation method according to claim 1, characterized in that, The mass ratio of nickel sulfate, sodium hypophosphite, lactic acid, propionic acid, sodium dodecyl sulfate, and thiourea is 27-34:16-24:16-24:6-10:(6-10)*10. -3 : (2-4)*10 -3 .

6. The preparation method according to claim 1, characterized in that, The post-processing includes filtering, washing, and drying the mixture.

Images