A method for nickel plating on the surface of diamond micropowder

Abstract

The present invention provides a method for nickel plating on the surface of diamond micropowder, comprising the following steps: pre-processing the diamond micropowder I; pre-processing the ceramic ball II; chemically nickel plating the diamond micropowder under ultrasonic and stirring conditions; and adding the ceramic ball during the chemical nickel plating process. The nickel-plated diamond microparticles prepared by the method provided by the present invention have a uniform and complete coating, a low leakage rate, and less agglomeration. Moreover, a wide range of diamond micropowders can be plated, and an effective coating can be plated for diamonds with a particle size in the range of 5-30 μm. The method provided by the present invention can effectively solve the adhesion problem of diamond micropowder in mass production of the prior art without affecting the quality of the coating.

Description

Technical Field

[0001] The invention belongs to the field of electroplating, and in particular relates to a method for plating nickel on the surface of diamond. Background Art

[0002] Treating the diamond surface can improve the various properties of diamond and thus extend its service life. For example, plating a layer of metal nickel on the diamond surface can give the diamond the following properties: improving the strength of the diamond, the interface bonding ability between the diamond and the matrix, oxygen isolation protection, reducing the degree of thermal damage to the diamond, improving the physical and chemical properties of the interface between the diamond and the matrix, and thus improving the wear resistance and cutting ability of the diamond tool.

[0003] Diamond surface nickel plating is usually achieved by chemical nickel plating. Chemical nickel plating is a method of depositing a nickel layer by using a redox reaction of a reducing agent on a catalytically active metal surface without an external current. Chemical plating is widely used because of its simple operation and low cost.

[0004] At present, the technology of chemical metal plating on diamond surface is relatively mature, such as the invention patent with publication number CN 112210771 A, which discloses a method of nickel plating on diamond surface. However, as the wire diameter of wire saws becomes smaller, the particle size of diamond micropowders that match it also becomes smaller. As the particle size of micropowders becomes smaller, the problems in the chemical nickel plating mass production process also gradually increase, such as excessive increase in particle size after plating and increased agglomeration. Summary of the invention

[0005] The object of the present invention is to provide a method for chemically plating nickel on the surface of diamond, which can effectively improve the agglomeration of diamond during the chemical nickel plating process, thereby effectively improving the product quality of diamond micropowder and the cutting effect of subsequent products.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for nickel plating on the surface of diamond micropowder comprises the following steps:

[0008] Pre-treatment of diamond powder Ⅰ;

[0009] Pre-treating the ceramic balls II;

[0010] Performing chemical nickel plating on the diamond micropowder under ultrasonic and stirring conditions;

[0011] The ceramic balls are added during the process of chemical nickel plating. Adding zirconium oxide balls in the early stage of chemical plating will cause the active points on the surface of diamond micropowder to fall off due to the collision between sand balls, affecting the deposition of the initial coating. In severe cases, it will cause large-area leakage plating on the surface of diamond micropowder.

[0012] The pretreatment I includes degreasing, pickling I, sensitization, activation and reduction processes.

[0013] The degreasing process includes washing with an inorganic alkaline solution and / or ultrasonic washing;

[0014] The inorganic alkali comprises sodium hydroxide, and the concentration of the inorganic alkali solution is 9-11wt%;

[0015] The ultrasonic washing time is 25-35min;

[0016] The pickling I comprises a process of ultrasonic washing with 10% to 30% inorganic acid under heating conditions;

[0017] The inorganic acid includes nitric acid;

[0018] The sensitizing solution used in the sensitization includes a hydrochloric acid solution of stannous chloride;

[0019] The sensitization time is 8-10min;

[0020] The activation solution used in the activation comprises a palladium chloride solution;

[0021] The activation time is 8-10min;

[0022] The reducing liquid used in the reduction process includes a sodium hypophosphite solution;

[0023] The sodium hypophosphite solution has a concentration of 20 g / L;

[0024] The reduction time is 9-11 minutes.

[0025] The pre-treatment II includes pickling II and water washing process;

[0026] The pickling II comprises the steps of heating with 30% nitric acid to 60°C and then soaking for 30-60 minutes;

[0027] Stirring once every 10 minutes during the heat preservation and soaking process;

[0028] The water washing includes the step of washing the ceramic balls to neutrality.

[0029] The chemical nickel plating comprises the steps of ultrasonically treating and stirring the diamond powder in a chemical plating solution and adding a chemical plating replenishing solution.

[0030] The chemical plating solution includes sodium citrate, lactic acid and nickel sulfate hexahydrate;

[0031] The concentration of sodium citrate in the chemical plating solution is 60-80 g / L;

[0032] The concentration of lactic acid in the chemical plating solution is 5-10 ml / L;

[0033] The concentration of nickel sulfate hexahydrate in the chemical plating solution is 90-110 g / L;

[0034] The chemical plating replenishing solution includes sodium hypophosphite and ammonia water;

[0035] The concentration of sodium hypophosphite in the chemical plating replenishing solution is 250-300 g / L;

[0036] The concentration of ammonia water in the chemical plating replenishing solution is 150-250 ml / L.

[0037] The method for plating nickel on the surface of diamond micropowder comprises the step of adding the ceramic ball at least 10 minutes after the start of chemical nickel plating.

[0038] The temperature of the chemical nickel plating is 40-60°C;

[0039] The particle size of the diamond powder is 7-8 μm;

[0040] The diameter of the ceramic ball is 2-6 mm;

[0041] The material of the ceramic ball includes oxide.

[0042] The oxide includes zirconium oxide.

[0043] Based on the atomic hydrogen state theory of chemical plating, the hypophosphite will undergo the following reaction

[0044]

[0045] 2H→H2

[0046] The oxygen vacancies on the surface of zirconium oxide will form dangling bonds with high energy. The dangling bonds can adsorb hypophosphite ions, which will make the above reaction tend to occur on the surface of the zirconium oxide ball. If the zirconium oxide ball is not added, the above reaction tends to occur on the surface of the diamond. The generation of hydrogen will affect the uniformity of the coating on the diamond surface. Therefore, adding zirconium oxide balls can make the coating on the diamond surface more uniform and increase the service life of diamond powder.

[0047] The added amount of the ceramic balls is 30-50% of the weight of the diamond powder.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The nickel-plated diamond microparticles prepared by the method provided by the present invention have uniform and complete coatings, low leakage rate and less agglomeration. Moreover, the diamond micropowders that can be plated have a wide range, and effective coatings can be plated for diamonds with a particle size in the range of 5-30 μm.

[0050] The method provided by the present invention can effectively solve the adhesion problem of diamond micropowder in batch production in the prior art without affecting the quality of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The electron microscope image of the diamond powder prepared in Comparative Example 1 is shown;

[0052] Figure 2 The particle size detection data of the diamond powder prepared in Comparative Example 1 is shown;

[0053] Figure 3 The electron microscope image of the diamond powder prepared in Example 1 is shown;

[0054] Figure 4 The electron microscope image of the diamond powder prepared in Example 1 is shown;

[0055] Figure 5 The particle size detection data of the diamond powder prepared in Example 1 is shown

[0056] Figure 6 The electron microscope image of the diamond powder prepared in Example 2 is shown;

[0057] Figure 7 The electron microscope image of the diamond powder prepared in Example 2 is shown;

[0058] Figure 8 The particle size detection data of the diamond powder prepared in Example 1 is shown;

[0059] Fig. 9 The electron microscope image of the diamond powder prepared in Example 3 is shown;

[0060] Fig.10 The electron microscope image of the diamond powder prepared in Example 3 is shown;

[0061] Fig.11 The particle size detection data of the diamond powder prepared in Example 3 is shown;

[0062] Fig.12 The electron microscope image of the diamond powder prepared in Comparative Example 2 is shown;

[0063] Fig.13 The electron microscope image of the diamond powder prepared in Comparative Example 2 is shown;

[0064] Fig.14 The particle size detection data of the diamond powder prepared in Comparative Example 2 is shown;

[0065] Fig.15The electron microscope image of the diamond powder prepared in Example 4 is shown;

[0066] Fig.16 The electron microscope image of the diamond powder prepared in Example 4 is shown;

[0067] Fig.17 The particle size detection data of the diamond powder prepared in Example 4 is shown;

[0068] Fig.18 An electron microscope image of the diamond powder prepared in Comparative Example 3 is shown. DETAILED DESCRIPTION

[0069] The present invention is further described below with reference to examples and comparative examples.

[0070] Comparative Example 1: No zirconia ball plating

[0071] Diamond powder (particle size 7-8 μm, 600 g) was processed in the following order:

[0072] 1. Pretreatment: degreasing, pickling, sensitization, activation and reduction of diamond powder

[0073] Degreasing: Soak in 10% sodium hydroxide solution at 55°C for 30 minutes; Wash with ultrasonic waves (ultrasonic frequency 30KHZ) for 30 minutes until neutral (pH 6-8);

[0074] Pickling: Place the degreased diamond in a 30% nitric acid solution, heat to 55°C and soak for 30 minutes, then use ultrasonic water washing for 30 minutes to clean until it becomes neutral;

[0075] Sensitization: Stir in sensitizing solution (60mL: stannous chloride 15g / L + hydrochloric acid: 30ml / L) for 10min, then wash twice with stirring water, each time with 2500mL of water;

[0076] Activation: Activate in activation solution (2000 mL, palladium chloride content is 0.1 g / L) for 10 min, stir and wash with water twice, each time using 3000 mL of water;

[0077] Reduction: Reduce in reducing solution (sodium hypophosphite: 30 g / L) for 10 min, then wash twice with stirring, using 3000 mL of water each time.

[0078] 2. Chemical nickel plating:

[0079] The composition of chemical plating solution A is: sodium citrate: 60g / L, lactic acid 7ml / L, nickel sulfate hexahydrate: 100g / L and ammonia water: 20ml / L;

[0080] The composition of chemical plating solution B is: sodium hypophosphite: 150g / L and ammonia water: 250ml / L.

[0081] (1) 600 g of diamond with a particle size of 7-8 μm was added into 15 L of chemical plating solution A. The sand bucket containing diamond and chemical plating solution A was placed in an ultrasonic water bath at 50°C and stirred continuously at a constant stirring speed of 120 rpm.

[0082] (2) Use a peristaltic pump to add additional chemical plating solution B to the sand bucket in step (1). After the chemical plating reaction begins, turn on the ultrasound (ultrasonic frequency is 20KHZ) and continue to add solution B. Stop adding after 120 minutes of plating. The chemical plating reaction temperature is 46±2°C and the pH value is 7.5±0.2. Continue stirring until the reaction stops.

[0083] (3) After continuous plating for 120 minutes, the diamond was cleaned and dried for particle size and electron microscopy testing.

[0084] Figure 1 This is an electron microscope image of the diamond powder prepared in Comparative Example 1. Figure 2 The particle size test data of the diamond powder prepared in Comparative Example 1. Figure 1 It can be seen that diamond agglomeration is more obvious after chemical plating. The reasons for diamond agglomeration during chemical plating are: 1. Due to the large specific surface area and high surface energy of diamond powder, diamond powders are easily attracted to each other to form soft agglomerates. These spontaneously formed agglomerates are not dispersed in time under mechanical stirring and ultrasonic vibration. In the subsequent chemical nickel plating process, they are gradually wrapped by the coating to form agglomerates as the coating grows; 2. The plated diamond micropowders are also easily agglomerated with each other in the subsequent reaction process due to the deposition growth of the coating.

[0085] Implementation 1

[0086] Diamond powder (particle size 7-8 μm, 600 g) was processed in the following order:

[0087] 1. Pretreatment: degreasing, pickling, sensitization, activation and reduction of diamond powder

[0088] Degreasing: Soak in 10% sodium hydroxide solution at 55°C for 30 minutes; Wash with ultrasonic waves (ultrasonic frequency 30KHZ) for 30 minutes until neutral (pH 6-8);

[0089] Pickling: Place the degreased diamond in a 30% nitric acid solution, heat to 55°C and soak for 30 minutes, then use ultrasonic water washing for 30 minutes to clean until it becomes neutral;

[0090] Sensitization: Stir in sensitizing solution (60mL: stannous chloride 15g / L + hydrochloric acid: 30ml / L) for 10min, then wash twice with stirring water, each time with 2500mL of water;

[0091] Activation: Activate in activation solution (2000 mL, palladium chloride content is 0.1 g / L) for 10 min, stir and wash with water twice, each time using 3000 mL of water;

[0092] Reduction: Reduce in reducing solution (sodium hypophosphite: 30 g / L) for 10 min, then wash twice with stirring, using 3000 mL of water each time.

[0093] 2. Chemical nickel plating:

[0094] The composition of chemical plating solution A is: sodium citrate: 60g / L, lactic acid 7ml / L, nickel sulfate hexahydrate: 100g / L and ammonia water: 20ml / L;

[0095] The composition of chemical plating solution B is: sodium hypophosphite: 150g / L and ammonia water: 250ml / L.

[0096] (1) 600 g of diamond with a particle size of 7-8 μm was added into 15 L of chemical plating solution A. The sand bucket containing diamond and chemical plating solution A was placed in an ultrasonic water bath at 50°C and stirred continuously at a constant stirring speed of 120 rpm.

[0097] (2) Use a peristaltic pump to add additional chemical plating solution B to the sand bucket in step (1). After the chemical plating reaction begins, turn on the ultrasound (ultrasonic frequency is 20KHZ) and continue to add solution B. Stop adding after 120 minutes of plating. The chemical plating reaction temperature is 46±2°C and the pH value is 7.5±0.2. Continue stirring until the reaction stops.

[0098] (3) 10 minutes after the start of the chemical plating reaction in step 2, 200 g of 5 mm zirconia balls were added, and the plating was continued for another 120 minutes;

[0099] (4) After the plating is completed, the zirconium oxide balls are screened out with a 200-mesh sieve, the plated diamonds are cleaned with pure water and dried, and the dried diamonds are then tested for particle size and electron microscopy.

[0100] Figure 3 and Figure 4 This is an electron microscope image of the diamond powder prepared in Example 1. Figure 5 The particle size test data of the diamond powder prepared in Example 1. Figure 3 and Figure 4It can be seen that the agglomerated diamonds are significantly reduced. The effects brought by the addition of zirconia spheres are as follows: 1. Under stirring and ultrasonic vibration, the zirconia spheres will separate the adsorbed diamond powders; 2. Since there are no active points on the surface of the zirconia spheres and they will not directly participate in chemical plating, the agglomeration of diamond powders caused by co-deposition of the coating when they attract each other during the plating process can be reduced; 3. The collision between the zirconia spheres and the plated diamonds will also separate the diamonds that are adhered together, thereby reducing the agglomeration of diamonds during the chemical plating process.

[0101] Implementation 2

[0102] Diamond powder (particle size 7-8 μm, 600 g) was processed in the following order:

[0103] 1. Pretreatment: degreasing, pickling, sensitization, activation and reduction of diamond powder

[0104] Degreasing: Soak in 10% sodium hydroxide solution at 55°C for 30 minutes; Wash with ultrasonic waves (ultrasonic frequency 30KHZ) for 30 minutes until neutral (pH 6-8);

[0105] Pickling: Place the degreased diamond in a 30% nitric acid solution, heat to 55°C and soak for 30 minutes, then use ultrasonic water washing for 30 minutes to clean until it becomes neutral;

[0106] Sensitization: Stir in sensitizing solution (60mL: stannous chloride 15g / L + hydrochloric acid: 30ml / L) for 10min, then wash twice with stirring water, each time with 2500mL of water;

[0107] Activation: Activate in activation solution (2000 mL, palladium chloride content is 0.1 g / L) for 10 min, stir and wash with water twice, each time using 3000 mL of water;

[0108] Reduction: Reduce in reducing solution (sodium hypophosphite: 30 g / L) for 10 min, then wash twice with stirring, using 3000 mL of water each time.

[0109] 2. Chemical nickel plating:

[0110] The composition of chemical plating solution A is: sodium citrate: 60g / L, lactic acid 7ml / L, nickel sulfate hexahydrate: 100g / L and ammonia water: 20ml / L;

[0111] The composition of chemical plating solution B is: sodium hypophosphite: 150g / L and ammonia water: 250ml / L.

[0112] (1) 600 g of diamond with a particle size of 7-8 μm was added into 15 L of chemical plating solution A. The sand bucket containing diamond and chemical plating solution A was placed in an ultrasonic water bath at 50°C and stirred continuously at a constant stirring speed of 120 rpm.

[0113] (2) Use a peristaltic pump to add additional chemical plating solution B to the sand bucket in step (1). After the chemical plating reaction begins, turn on the ultrasound (ultrasonic frequency is 20KHZ) and continue to add solution B. Stop adding after 120 minutes of plating. The chemical plating reaction temperature is 46±2°C and the pH value is 7.5±0.2. Continue stirring until the reaction stops.

[0114] (3) 10 minutes after the start of the chemical plating reaction in step 2, 300 g of 5 mm zirconia balls were added, and the plating was continued for another 120 minutes.

[0115] (4) After the plating is completed, the zirconium oxide balls are screened out with a 200-mesh sieve, the plated diamonds are cleaned with pure water and dried, and the dried diamonds are then tested for particle size and electron microscopy.

[0116] Figure 6 and Figure 7 This is an electron microscope image of the diamond powder prepared in Example 2. Figure 8 The particle size test data of the diamond powder prepared in Example 2. Figure 6 and Figure 7 It can be seen that there is no obvious agglomeration of diamonds, but there is slight plating leakage. The possible reasons are: the increase in the weight of the zirconia balls can still effectively control the agglomeration of diamonds, but with the increase in the number of zirconia balls, the collision probability between the zirconia balls and diamonds and the probability of plating deposition barrier both increase accordingly. Excessive collision and barrier will destroy the normal deposition of the coating, resulting in final plating leakage.

[0117] Implementation 3

[0118] Diamond powder (particle size 7-8 μm, 600 g) was processed in the following order:

[0119] 1. Pretreatment: degreasing, pickling, sensitization, activation and reduction of diamond powder

[0120] Degreasing: Soak in 10% sodium hydroxide solution at 55°C for 30 minutes; Wash with ultrasonic waves (ultrasonic frequency 30KHZ) for 30 minutes until neutral (pH 6-8);

[0121] Pickling: Place the degreased diamond in a 30% nitric acid solution, heat to 55°C and soak for 30 minutes, then use ultrasonic water washing for 30 minutes to clean until it becomes neutral;

[0122] Sensitization: Stir in sensitizing solution (60mL: stannous chloride 15g / L + hydrochloric acid: 30ml / L) for 10min, then wash twice with stirring water, each time with 2500mL of water;

[0123] Activation: Activate in activation solution (2000 mL, palladium chloride content is 0.1 g / L) for 10 min, stir and wash with water twice, each time using 3000 mL of water;

[0124] Reduction: Reduce in reducing solution (sodium hypophosphite: 30 g / L) for 10 min, then wash twice with stirring, using 3000 mL of water each time.

[0125] 2. Chemical nickel plating:

[0126] The composition of chemical plating solution A is: sodium citrate: 60g / L, lactic acid 7ml / L, nickel sulfate hexahydrate: 100g / L and ammonia water: 20ml / L;

[0127] The composition of chemical plating solution B is: sodium hypophosphite: 150g / L and ammonia water: 250ml / L.

[0128] (1) 600 g of diamond with a particle size of 7-8 μm was added into 15 L of chemical plating solution A. The sand bucket containing diamond and chemical plating solution A was placed in an ultrasonic water bath at 50°C and stirred continuously at a constant stirring speed of 120 rpm.

[0129] (2) Use a peristaltic pump to add additional chemical plating solution B to the sand bucket in step (1). After the chemical plating reaction begins, turn on the ultrasound (ultrasonic frequency is 20KHZ) and continue to add solution B. Stop adding after 120 minutes of plating. The chemical plating reaction temperature is 46±2°C and the pH value is 7.5±0.2. Continue stirring until the reaction stops.

[0130] (3) 10 minutes after the start of the chemical plating reaction in step 2, 300 g of 3 mm zirconia balls were added, and the plating was continued for another 120 minutes.

[0131] (4) After the plating is completed, the zirconium oxide balls are screened out with a 200-mesh sieve, the plated diamonds are cleaned with pure water and dried, and the dried diamonds are then tested for particle size and electron microscopy.

[0132] Fig. 9 and Fig.10 This is an electron microscope image of the diamond powder prepared in Example 3. Fig.11 The particle size test data of the diamond powder prepared in Example 3. Figure 6 and Figure 7It can be seen that the agglomerated diamonds are significantly reduced compared to those without zirconia balls, but there is a slight single missed plating. The possible reasons are: the increase in the weight of the zirconia balls can still effectively control the agglomeration of diamonds, but with the increase in the number of zirconia balls, the collision probability between the zirconia balls and diamonds and the probability of barrier coating deposition are increased accordingly. Excessive collision and barrier will destroy the normal deposition of the coating, resulting in missed coating in the end.

[0133] Comparative Example 2

[0134] Diamond powder (particle size 7-8 μm, 600 g) was processed in the following order:

[0135] 1. Pretreatment: degreasing, pickling, sensitization, activation and reduction of diamond powder

[0136] Degreasing: Soak in 10% sodium hydroxide solution at 55°C for 30 minutes; Wash with ultrasonic waves (ultrasonic frequency 30KHZ) for 30 minutes until neutral (pH 6-8);

[0137] Pickling: Place the degreased diamond in a 30% nitric acid solution, heat to 55°C and soak for 30 minutes, then use ultrasonic water washing for 30 minutes to clean until it becomes neutral;

[0138] Sensitization: Stir in sensitizing solution (60mL: stannous chloride 15g / L + hydrochloric acid: 30ml / L) for 10min, then wash twice with stirring water, each time with 2500mL of water;

[0139] Activation: Activate in activation solution (2000 mL, palladium chloride content is 0.1 g / L) for 10 min, stir and wash with water twice, each time using 3000 mL of water;

[0140] Reduction: Reduce in reducing solution (sodium hypophosphite: 30 g / L) for 10 min, then wash twice with stirring, using 3000 mL of water each time.

[0141] 2. Chemical nickel plating:

[0142] The composition of chemical plating solution A is: sodium citrate: 60g / L, lactic acid 7ml / L, nickel sulfate hexahydrate: 100g / L and ammonia water: 20ml / L;

[0143] The composition of chemical plating solution B is: sodium hypophosphite: 150g / L and ammonia water: 250ml / L.

[0144] (1) 600 g of diamond with a particle size of 7-8 μm was added into 15 L of chemical plating solution A. The sand bucket containing diamond and chemical plating solution A was placed in an ultrasonic water bath at 50°C and stirred continuously at a constant stirring speed of 120 rpm.

[0145] (2) Use a peristaltic pump to add additional chemical plating solution B to the sand bucket in step (1). After the chemical plating reaction begins, turn on the ultrasound (ultrasonic frequency is 20KHZ) and continue to add solution B. Stop adding after 120 minutes of plating. The chemical plating reaction temperature is 46±2°C and the pH value is 7.5±0.2. Continue stirring until the reaction stops.

[0146] (3) 10 minutes after the start of the chemical plating reaction in step 2, 200 g of 3 mm zirconia balls were added, and the plating was continued for another 120 minutes.

[0147] (4) After the plating is completed, the zirconium oxide balls are screened out with a 200-mesh sieve, the plated diamonds are cleaned with pure water and dried, and the dried diamonds are then tested for particle size and electron microscopy.

[0148] Fig.12 and Fig.13 This is an electron microscope image of the diamond powder prepared in Comparative Example 2. Fig.14 The particle size detection data of the diamond powder prepared in Comparative Example 2. From the above electron microscope pictures, compared with no zirconia balls, the diamond agglomeration is significantly reduced after adding 3mm and 200g zirconia balls, but small agglomerates still exist. The possible reasons are: the reduction of the size and weight of the zirconia balls can still effectively reduce the agglomeration of diamonds, but with the reduction of the number and weight of the zirconia balls, the collision probability of the zirconia balls and diamonds and the probability of the deposition of the coating are correspondingly reduced.

[0149] Implementation 4

[0150] Diamond powder (particle size 28 μm, 1000 g) was processed in the following order:

[0151] 1. Pretreatment: degreasing, pickling, sensitization, activation and reduction of diamond powder

[0152] Degreasing: Soak in 10% sodium hydroxide solution at 55°C for 30 minutes; Wash with ultrasonic waves (ultrasonic frequency 30KHZ) for 30 minutes until neutral (pH 6-8);

[0153] Pickling: Place the degreased diamond in a 30% nitric acid solution, heat to 55°C and soak for 30 minutes, then use ultrasonic water washing for 30 minutes to clean until it becomes neutral;

[0154] Sensitization: Stir in sensitizing solution (60mL: stannous chloride 15g / L + hydrochloric acid: 30ml / L) for 10min, then wash twice with stirring water, each time with 2500mL of water;

[0155] Activation: Activate in activation solution (2000 mL, palladium chloride content is 0.1 g / L) for 10 min, stir and wash with water twice, each time using 3000 mL of water;

[0156] Reduction: Reduce in reducing solution (sodium hypophosphite: 30 g / L) for 10 min, then wash twice with stirring, using 3000 mL of water each time.

[0157] 2. Chemical nickel plating:

[0158] The composition of chemical plating solution A is: sodium citrate: 60g / L, lactic acid 7ml / L, nickel sulfate hexahydrate: 100g / L and ammonia water: 20ml / L;

[0159] The composition of chemical plating solution B is: sodium hypophosphite: 150g / L and ammonia water: 250ml / L.

[0160] (1) 1000 g of diamond with a particle size of 28 μm that has been processed previously is put into 15 L of chemical plating solution A, and the sand bucket containing diamond and chemical plating solution A is placed in an ultrasonic water bath at 50°C and stirred continuously at a constant stirring speed of 120 rpm;

[0161] (2) Use a peristaltic pump to add additional chemical plating solution B to the sand bucket in step (1). After the chemical plating reaction begins, turn on the ultrasound (ultrasonic frequency is 20KHZ) and continue to add solution B. Stop adding after 120 minutes of plating. The chemical plating reaction temperature is 46±2°C and the pH value is 7.5±0.2. Continue stirring until the reaction stops.

[0162] (3) 10 minutes after the start of the chemical plating reaction in step 2, 300 g of 5 mm zirconia balls were added, and the plating was continued for another 120 minutes.

[0163] (4) After the plating is completed, the zirconium oxide balls are screened out with a 200-mesh sieve, the plated diamonds are cleaned with pure water and dried, and the dried diamonds are then tested for particle size and electron microscopy.

[0164] Fig.15 and Fig.16 This is an electron microscope image of the diamond powder prepared in Example 4. Fig.17 The particle size detection data of the diamond powder prepared in Example 4.

[0165]

[0166] Comparative Example 3

[0167] Diamond powder (particle size 7-8 μm, 600 g) was processed in the following order:

[0168] 1. Pretreatment: degreasing, pickling, sensitization, activation and reduction of diamond powder

[0169] Degreasing: Soak in 10% sodium hydroxide solution at 55°C for 30 minutes; Wash with ultrasonic waves (ultrasonic frequency 30KHZ) for 30 minutes until neutral (pH 6-8);

[0170] Pickling: Place the degreased diamond in a 30% nitric acid solution, heat to 55°C and soak for 30 minutes, then use ultrasonic water washing for 30 minutes to clean until it becomes neutral;

[0171] Sensitization: Stir in sensitizing solution (60mL: stannous chloride 15g / L + hydrochloric acid: 30ml / L) for 10min, then wash twice with stirring water, each time with 2500mL of water;

[0172] Activation: Activate in activation solution (2000 mL, palladium chloride content is 0.1 g / L) for 10 min, stir and wash with water twice, each time using 3000 mL of water;

[0173] Reduction: Reduce in reducing solution (sodium hypophosphite: 30 g / L) for 10 min, then wash twice with stirring, using 3000 mL of water each time.

[0174] 2. Chemical nickel plating:

[0175] The composition of chemical plating solution A is: sodium citrate: 60g / L, lactic acid 7ml / L, nickel sulfate hexahydrate: 100g / L and ammonia water: 20ml / L;

[0176] The composition of chemical plating solution B is: sodium hypophosphite: 150g / L and ammonia water: 250ml / L.

[0177] (1) 600 g of diamond with a particle size of 7-8 μm was added into 15 L of chemical plating solution A. The sand bucket containing diamond and chemical plating solution A was placed in an ultrasonic water bath at 50°C and stirred continuously at a constant stirring speed of 120 rpm.

[0178] (2) Use a peristaltic pump to add additional chemical plating solution B to the sand bucket in step (1). After the chemical plating reaction begins, turn on the ultrasound (ultrasonic frequency is 20KHZ) and continue to add solution B. Stop adding after 120 minutes of plating. The chemical plating reaction temperature is 46±2°C and the pH value is 7.5±0.2. Continue stirring until the reaction stops.

[0179] (3) 10 minutes after the start of the chemical plating reaction in step 2, 200 g of 5 mm zirconium nitride balls were added and the plating was continued for another 120 minutes.

[0180] Fig.18The surface morphology of the diamond powder prepared in Comparative Example 3 is shown. As can be seen from the figure, the coating uniformity on the surface of the diamond powder is poor. This is because there are no oxygen vacancies on the surface of zirconium nitride, which cannot adsorb hypophosphite ions, resulting in hydrogen generated on the surface of the diamond powder, thereby deteriorating the coating uniformity.

Claims

1. A method for nickel plating on the surface of diamond micropowder, characterized in that: The steps include: Pre-treatment of diamond powder Ⅰ; Pre-treating the ceramic balls II; Performing chemical nickel plating on the diamond micropowder under ultrasonic and stirring conditions; Add the ceramic ball at least 10 minutes after the start of chemical nickel plating; The diameter of the ceramic ball is 2-6 mm; The pre-treatment I includes degreasing, pickling I, sensitization, activation and reduction processes; The pre-treatment II includes pickling II and water washing process; The particle size of the diamond powder is 7-8 μm.

2. The method for nickel plating on the surface of diamond micropowder as claimed in claim 1, characterized in that: The degreasing process includes washing with an inorganic alkaline solution and / or ultrasonic washing; The inorganic alkali comprises sodium hydroxide, and the concentration of the inorganic alkali solution is 9-11wt%; The ultrasonic washing time is 25-35min; The pickling I comprises a process of ultrasonic washing with 10% to 30% inorganic acid under heating conditions; The inorganic acid includes nitric acid; The sensitizing solution used in the sensitization includes a hydrochloric acid solution of stannous chloride; The sensitization time is 8-10min; The activation solution used in the activation comprises a palladium chloride solution; The activation time is 8-10min; The reducing liquid used in the reduction process includes a sodium hypophosphite solution; The sodium hypophosphite solution has a concentration of 20 g / L; The reduction time is 9-11 minutes.

3. The method for nickel plating on the surface of diamond powder as claimed in claim 1, characterized in that: The pickling II comprises the steps of heating with 30% nitric acid to 60°C and then soaking for 30-60 minutes; Stirring once every 10 minutes during the heat preservation and soaking process; The water washing includes the step of washing the ceramic balls to neutrality.

4. The method for nickel plating on the surface of diamond micropowder as claimed in claim 1, characterized in that: The chemical nickel plating comprises the steps of ultrasonically treating and stirring the diamond powder in a chemical plating solution and adding a chemical plating replenishing solution.

5. The method for nickel plating on the surface of diamond micropowder as claimed in claim 4, characterized in that: The chemical plating solution includes sodium citrate, lactic acid and nickel sulfate hexahydrate; The concentration of sodium citrate in the chemical plating solution is 60-80 g / L; The concentration of lactic acid in the chemical plating solution is 5-10 ml / L; The concentration of nickel sulfate hexahydrate in the chemical plating solution is 90-110 g / L; The chemical plating replenishing solution includes sodium hypophosphite and ammonia water; The concentration of sodium hypophosphite in the chemical plating replenishing solution is 250-300 g / L; The concentration of ammonia water in the chemical plating replenishing solution is 150-250 ml / L.

6. The method for nickel plating on the surface of diamond micropowder as claimed in claim 1, characterized in that: The temperature of the chemical nickel plating is 40-60°C.

7. The method for nickel plating on the surface of diamond powder as claimed in claim 1, characterized in that: The added amount of the ceramic balls is 30-50% of the weight of the diamond powder.

8. The method for nickel plating on the surface of diamond micropowder as claimed in claim 1, characterized in that: The material of the ceramic ball includes oxide; The oxide includes zirconium oxide.

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