A method for tungsten plating on the surface of diamond

Abstract

The present invention relates to the field of coating technology, and particularly to a method for plating tungsten on the surface of diamond. The method of the present invention comprises the following steps: roughening diamond particles to obtain roughened diamond particles; mixing the roughened diamond particles with a colloidal palladium solution for sensitization-activation, and then mixing the sensitized-activated diamond particles with a peptizing solution for peptization to obtain activated diamond particles; mixing the activated diamond particles with a plating material, and subjecting the obtained mixture to a plating reaction in a hydrogen atmosphere to form a coating on the surface of the diamond; the component of the coating is W and WC; the temperature of the plating reaction is 700-800 °C; the plating material is blue tungsten or violet tungsten. The present invention can form a coating on the surface of diamond at a relatively low temperature, avoiding thermal damage to the diamond; the coating is dense and uniform, without any phenomenon of missing plating, and the cost is relatively low.

Description

Technical Field

[0001] The present invention relates to the field of coating technology, and particularly to a method for tungsten plating on the surface of diamond. Background Art

[0002] Diamond has the highest thermal conductivity (1200 - 2000 W·m -1 ·K -1 ) among natural materials. As the second phase, the diamond - Cu composite material obtained by compounding with highly thermally conductive metal copper can theoretically obtain extremely excellent thermal conductivity performance. Therefore, it has become a research hotspot as the most potential new generation of thermal management materials for electronic packaging. However, due to the poor wettability between diamond and copper phases, developing or optimizing a feasible interface optimization method has become the core of related research work.

[0003] To improve the wettability between diamond and copper, tungsten plating on the surface of diamond is an effective method. Among the carbides corresponding to the currently selectable plating elements, the WC formed by tungsten and the carbon atoms on the diamond surface has the highest thermal conductivity value, up to 121 W·m -1 ·K -1 , and at 1150 °C, the wetting angle of copper to WC is the smallest, only 17°, which can significantly increase the wettability between diamond and copper.

[0004] However, there are also technical difficulties in coating a uniform and dense tungsten film on the surface of diamond. The existing tungsten coating methods mainly include magnetron sputtering, chemical vapor deposition, salt bath plating and powder coating sintering, but the existing tungsten coating methods all have different disadvantages and limitations. Lu Qingyuan proposed the magnetron sputtering method in "Method for forming chemically bonded metal coating on diamond particles" (CN1752267A). Although this method can coat tungsten on the surface of diamond particles, the single coating amount of this method is small, the obtained film thickness is uneven, and there will be a phenomenon of leakage of plating on a certain crystal face of diamond or even part of the diamond particles, especially when the size of the diamond particles is small, the leakage phenomenon is more serious; at the same time, this method requires special equipment, low production efficiency, special target materials, and special operation. Ma Jie et al. used chemical deposition to plate tungsten on the surface of diamond at 550-700°C in "A method for plating tungsten on the surface of diamond powder" (CN 106521451A). The coating temperature of this process is low and does not cause thermal damage to diamond, but the coating phase is W, and diamond and tungsten do not form a metallurgical bond of WC. Yu Xinquan et al. used salt bath plating to plate tungsten on the surface of diamond in "A method for plating tungsten on the surface of diamond" (CN 103388142 A), but the plating temperature is high (900-1000°C), which is easy to cause thermal damage to diamond. Wang Xitao et al. used diamond covering combustion method to plate tungsten in "A method for preparing a new type of high thermal conductivity copper-based composite material" (CN 104651658 A) to obtain a coating composed of W phase and WC phase, but the plating temperature is high (up to 950-1050°C), which is easy to cause thermal damage to diamond. Xiang Bo proposed a new method (Xiang Bo, Xie Zhigang, He Yuehui, et al. A new method for coating tungsten on diamond surface [J]. The Chinese Journal of Nonferrous Metals, 2007, 17(9): 1511-1515.), which is to use H 2 / H 2 O mixed gas at 750℃~900℃ reduces tungsten oxide containing catalyst, and uses tungsten oxide to evaporate in water vapor and chemical vapor transmission to plate tungsten on the diamond surface. The tungsten film obtained by this method has serious leakage plating phenomenon. The above analysis shows that the method of tungsten plating on the diamond surface needs to be further improved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for plating tungsten on a diamond surface, which can form a coating on the diamond surface at a relatively low temperature to avoid heat loss of the diamond; the coating is dense and uniform, without leakage, and has a low cost.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for plating tungsten on a diamond surface, comprising the following steps:

[0008] The diamond particles are roughened to obtain roughened diamond particles;

[0009] The roughened diamond particles are mixed with a colloidal palladium solution for sensitization-activation, and then the sensitized-activated diamond particles are mixed with a peptizing solution for peptization to obtain activated diamond particles;

[0010] The activated diamond particles are mixed with a plating material, and the obtained mixture is subjected to a plating reaction in a hydrogen atmosphere to form a coating on the diamond surface; the coating is composed of W and WC; the temperature of the plating reaction is 700-800 °C; the plating material is blue tungsten or violet tungsten.

[0011] Preferably, the time of the plating reaction is 30-180 min.

[0012] Preferably, the particle size of the diamond particles is 20-600 μm.

[0013] Preferably, the particle size of the blue tungsten or violet tungsten is 20-1000 nm.

[0014] Preferably, the mass ratio of the activated diamond particles to the plating material is 1:(0.2-2).

[0015] Preferably, after the plating reaction is completed, it further includes screening and separating the reaction product to obtain tungsten-plated diamonds and tungsten powder.

[0016] Preferably, the method of the roughening treatment is: boiling the diamond particles in a nitric acid solution for 3-10 min; the mass fraction of the nitric acid solution is 30%.

[0017] Preferably, the raw materials for preparing the colloidal palladium solution include: palladium chloride 1 g / L, stannous chloride 77.53 g / L, sodium stannate 7 g / L, hydrochloric acid 300 mL / L and the balance of water; the mass fraction of the hydrochloric acid is 36-38%.

[0018] Preferably, the time of the sensitization-activation is 3-6 min.

[0019] Preferably, the peptizing solution is dilute hydrochloric acid or sodium hypophosphite solution; the mass fraction of the dilute hydrochloric acid is 10%, and the concentration of the sodium hypophosphite solution is 20-30 g / L.

[0020] The present invention provides a method for tungsten plating on the surface of diamond, comprising the following steps: roughening diamond particles to obtain roughened diamond particles; mixing the roughened diamond particles with a colloidal palladium solution for sensitization-activation, and then mixing the sensitized-activated diamond particles with a peptizing solution for peptization to obtain activated diamond particles; mixing the activated diamond particles with a plating material, and subjecting the obtained mixture to a plating reaction under a hydrogen atmosphere to form a coating on the surface of the diamond; the coating is composed of W and WC; the temperature of the plating reaction is 700-800 °C; the plating material is blue tungsten or violet tungsten.

[0021] The present invention forms micro-etch pits on the surface of diamond by roughening treatment, which is convenient for subsequent tungsten plating on diamond; then the obtained roughened diamond particles are mixed with a colloidal palladium solution for sensitization-activation to adsorb colloidal palladium microparticles on the surface of the diamond particles, and then mixed with a peptizing solution for peptization to obtain activated diamond particles adsorbed with palladium active sites; finally, the activated diamond particles adsorbed with palladium active sites are mixed with a plating material. Using blue tungsten or violet tungsten as the plating material, due to the strong reactivity of blue tungsten and violet tungsten, at a relatively low temperature (700-800 °C), blue tungsten or violet tungsten can undergo a reduction reaction with hydrogen, and the generated active W atoms migrate with the gas phase and come into full contact with the surface of the diamond. At the same time, the palladium active sites existing on the surface of the activated diamond are conducive to the deposition of tungsten on the surface of the diamond; according to the crystal structure of diamond, there is a dangling bond on the surface carbon atoms of diamond, and this dangling bond can undergo an interfacial bonding reaction with strong carbide-forming elements such as W at the plating temperature to generate stable WC. During the plating process, with the diffusion and migration of C and W atoms on the surface of the diamond, W and C with relatively close physical distances combine to react and generate WC. As the reaction proceeds, the generated WC layer hinders the further diffusion and migration of C and W, and part of the W atoms are deposited on the surface of the coating in the form of metallic W. Therefore, a uniform and dense coating can be formed on the surface of the diamond after diffusion tungsten plating, and the coating phase is composed of W and WC.

[0022] The plating reaction temperature of the present invention is relatively low (700-800 °C), so thermal damage to the diamond can be avoided. In addition, because the reaction temperature of the traditional tungsten plating method is high, it is not easy to control the coating thickness. When the coating is relatively thick, stress concentration is likely to occur at the edges and corners of the diamond surface, resulting in coating peeling off. At the same time, the interfacial stress difference between the coating and the diamond substrate is also likely to cause coating peeling; the present invention performs sensitization-activation treatment on the diamond, making the diamond particles easily adsorb the active W atoms generated during the plating process. At the same time, by using low-temperature active plating, the coating thickness can be controlled within 100 nm, and the stress difference between the coating and the diamond is relatively small, so there is no phenomenon of missed plating.

[0023] The method of the present invention can effectively coat diamonds with a particle size range of 20 - 600 μm, and has a wider coating range. This is because the coating temperature of the salt bath plating and powder covering sintering methods is generally above 900 °C. After the reaction between the diamond and the coating material, there will be a bonding phenomenon, and agglomeration will also occur between the coating material particles, making it impossible to effectively separate the diamonds. It is not suitable for coating diamonds with a mesh size below 200. However, the coating temperature of the present invention is relatively low, which can reduce the bonding between the coating material and the diamond, avoid the agglomeration between the coating material particles, and the separation of the diamonds can be achieved only through simple screening. The screening is simple, so the coating range is wider.

[0024] The product of the coating reaction of the present invention is tungsten-coated diamond and tungsten powder. The tungsten powder has a high commercial value, reducing the coating cost.

[0025] The tungsten-coated diamond obtained by the method of the present invention can be applied to the preparation of diamond-Cu high thermal conductivity materials. At the same time, after tungsten coating, the resistivity of the diamond drops significantly. Especially for diamond micropowder with a mesh size of 400, the resistivity drops to 3.4×10 -2 Ω·cm, which can be used for the preparation of precision grinding tools with requirements for diamond conductivity.

[0026] The coating method of the present invention requires simple equipment, is easy to operate, does not produce harmful substances, and can be used for industrial production. Description of the Drawings

[0027] Figure 1 SEM image of diamond after tungsten coating in Example 1;

[0028] Figure 2 SEM image of the surface coating of tungsten-coated diamond in Example 1;

[0029] Figure 3 XRD pattern of tungsten-coated diamond in Example 1. Detailed Embodiment

[0030] The present invention provides a method for coating tungsten on the surface of diamond, which includes the following steps:

[0031] Roughen the diamond particles to obtain roughened diamond particles;

[0032] Mix the roughened diamond particles with a colloidal palladium solution for sensitization-activation, and then mix the sensitized-activated diamond particles with a peptizing solution for peptization to obtain activated diamond particles;

[0033] Mix the activated diamond particles with a coating material, and carry out a coating reaction on the obtained mixture under a hydrogen atmosphere to form a coating on the surface of the diamond; the composition of the coating is W and WC; the temperature of the coating reaction is 700 - 800 °C; the coating material is blue tungsten or purple tungsten.

[0034] In the present invention, unless otherwise specified, the raw materials used are commercially available products well-known in the art.

[0035] In the present invention, the diamond particles are roughened to obtain roughened diamond particles. In the present invention, the particle size of the diamond particles is preferably 20 - 600 μm. Diamond particles with different particle sizes have different uses, and those skilled in the art can select diamond particles with appropriate particle sizes according to the use of the diamond particles. In the present invention, the method of roughening treatment is preferably: boiling the diamond particles in a nitric acid solution for 3 - 10 min; the mass fraction of the nitric acid solution is preferably 30%. In the present invention, the dosage ratio of the diamond particles to nitric acid is preferably 10 g : (50 - 100) mL. The present invention forms micro-etch pits on the surface of the diamond by roughening treatment, which is convenient for subsequent tungsten plating on the diamond.

[0036] Before the roughening treatment, the present invention preferably further includes removing oil stains from the diamond particles. In the present invention, the method of removing oil stains preferably includes the following steps: placing the diamond particles in a NaOH solution, ultrasonically oscillating and cleaning for 20 - 40 min, taking them out and washing with deionized water until neutral; then placing the washed diamond particles in an HCl solution and soaking for 10 - 30 min, taking them out and washing with deionized water until neutral. In the present invention, the mass concentration of the NaOH solution is preferably 5 - 10%; the mass fraction of the HCl solution is preferably 5 - 10%. The present invention has no special requirements for the power of the ultrasonic oscillation, and the ultrasonic oscillation power well-known in the art can be used. In the present invention, the dosage ratio of the diamond particles to the NaOH solution is preferably 10 g : 50 - 100 mL; the dosage ratio of the diamond particles to HCl is preferably 10 g : 50 - 100 mL;

[0037] After obtaining the roughened diamond particles, the present invention mixes the roughened diamond particles with a colloidal palladium solution for sensitization - activation, and then mixes the sensitized - activated diamond particles with a peptizing solution for peptization to obtain activated diamond particles.

[0038] In the present invention, the raw materials for preparing the colloidal palladium solution preferably include: palladium chloride 1 g / L, stannous chloride 77.53 g / L, sodium stannate 7 g / L, hydrochloric acid 300 mL / L, and the balance of water. In the present invention, the mass fraction of the hydrochloric acid is preferably 36 - 38%; the hydrochloric acid is preferably analytical pure hydrochloric acid.

[0039] The present invention has no special requirements for the preparation method of the colloidal palladium solution, and it can be prepared by using the well-known preparation methods in the art. Taking the preparation of 1 L of colloidal palladium solution as an example, the preparation method of the colloidal palladium solution preferably includes the following steps: Add 75 g of stannous chloride to 200 mL of analytical pure hydrochloric acid, stir until completely dissolved, then add 7 g of sodium stannate and stir to prepare solution B; Mix 100 mL of analytical pure hydrochloric acid with 200 mL of distilled water, stir evenly, then add 1 g of palladium chloride and stir, and then add 2.53 g of stannous chloride, stir to make it react fully and dissolve for 10 - 15 min to prepare solution A; Slowly add solution B to solution A, place the obtained mixed solution in an aqueous solution at 40 - 50 °C and keep it warm for 3 - 4 h, and then add an appropriate amount of deionized water to dilute the solution to 1 L to obtain the colloidal palladium solution.

[0040] The present invention has no special requirements for the stirring rate and time of the above-mentioned stirring, and it is only necessary to make each substance mix evenly. During the preparation of solution B in the present invention, only physical changes occur to each substance, and solution B is a white emulsion. The present invention slowly adds solution B to solution A. In an acidic solution, Pd 2+ reacts with Sn 2+ to generate adsorptive colloidal palladium particles, and adsorb the excessive Sn 2+ in the solution, and exist in a colloidal form. The present invention has no special requirements for the addition rate of solution B, and it can be added dropwise at a well-known rate in the art. Slowly adding is to maintain the stability of the solution.

[0041] The present invention mixes the roughened diamond particles with the colloidal palladium solution for sensitization - activation to obtain diamond particles adsorbed with colloidal palladium particles. In the present invention, the time for sensitization - activation is preferably 3 - 10 min, more preferably 5 - 8 min. In the present invention, the sensitization - activation is preferably carried out under stirring conditions. The present invention has no special requirements for the stirring rate, and a well-known stirring rate in the art can be used. During the sensitization - activation process in the present invention, colloidal palladium particles are adsorbed on the surface of the diamond particles.

[0042] After completing the sensitization - activation, the present invention preferably further includes washing the sensitized - activated diamond particles with deionized water until neutral to obtain diamond particles adsorbed with colloidal palladium particles.

[0043] After obtaining the diamond particles adsorbed with colloidal palladium particles, the present invention mixes the diamond particles adsorbed with colloidal palladium particles with a peptizing solution for peptization to obtain activated diamond particles.

[0044] In the present invention, the peptizing solution is preferably dilute hydrochloric acid or sodium hypophosphite solution; the mass fraction of the dilute hydrochloric acid is preferably 10%, and the concentration of the sodium hypophosphite solution is preferably 20 - 30 g / L, more preferably 22 - 28 g / L. The present invention has no special requirements for the mixing method, and any mixing method well-known in the art can be used. In the present invention, the peptizing time is preferably 3 - 5 min; the peptizing is preferably carried out under stirring conditions. The present invention has no special requirements for the stirring rate, and any stirring rate well-known in the art can be used. During the peptizing process of the present invention, the peptizing solution reacts with the hydrolyzed glue layer adsorbed around the colloidal palladium to expose the catalytically active metal palladium particles, and activated diamond particles adsorbed with palladium active sites are obtained. 2+ 、Sn 4+ hydrolyzes the glue layer reaction to expose the catalytically active metal palladium particles, and activated diamond particles adsorbed with palladium active sites are obtained.

[0045] After completing the peptizing, the present invention preferably further includes washing the peptized diamond particles with deionized water until neutral, then washing with acetone or alcohol for 5 - 10 min, finally washing with deionized water, and drying in an oven at 100 °C to obtain activated diamond particles.

[0046] After obtaining the activated diamond particles, the present invention mixes the activated diamond particles with the plating material, and performs a plating reaction on the obtained mixture in a hydrogen atmosphere to form a coating on the diamond surface.

[0047] In the present invention, the plating material is blue tungsten or violet tungsten, and the particle size of the plating material is preferably 20 - 1000 nm, more preferably 30 - 800 nm, further preferably 40 - 600 nm, and most preferably 50 - 200 nm. By controlling the particle size of the plating material within the above range in the present invention, the plating material has higher reaction activity. In the present invention, the mass ratio of the activated diamond particles to the plating material is preferably 1:(0.2 - 2), more preferably 1:(0.5 - 1). The present invention has no special requirements for the mixing method, and any method capable of uniformly mixing the activated diamond particles and the plating material can be used.

[0048] In the present invention, the temperature of the plating reaction is preferably 700 - 800 °C, more preferably 730 - 780 °C; the time of the plating reaction is preferably 30 - 180 min, more preferably 60 - 120 min. In the present invention, the plating reaction is preferably carried out in a tubular furnace, and the present invention preferably places the mixture in a porcelain boat and then places it in the tubular furnace to carry out the plating reaction.

[0049] The present invention uses blue tungsten or violet tungsten as the plating material. Blue tungsten or violet tungsten has strong reactivity and can react with hydrogen at a relatively low temperature for reduction reaction, thus avoiding thermal damage to diamond particles caused by high temperature. During the plating reaction process of the present invention, blue tungsten or violet tungsten reacts with hydrogen to generate reduction reaction, and the generated tungsten atoms migrate with the gas phase and come into full contact with the diamond surface. At the same time, the palladium active sites existing on the activated diamond surface are conducive to the deposition of tungsten on the diamond surface and the formation of a coating; after diffusion tungsten plating, a uniform and dense coating can be formed on the diamond surface. The present invention sensitizes - activates and desizes the diamond, making the diamond particles easy to adsorb the active W atoms generated during the plating process. At the same time, low - temperature active plating can control the coating thickness within 100 nm, and the stress difference between the coating and the diamond is small, so there is no phenomenon of missed plating.

[0050] After the plating reaction of the present invention, the reaction product obtained is tungsten - plated diamond and tungsten powder. The tungsten - plated diamond includes diamond and a coating attached to the diamond surface, and the phase of the coating is composed of W and WC.

[0051] After completing the plating reaction, the present invention preferably cools the reaction system to room temperature with the furnace, and screens and separates the plating reaction product to obtain tungsten - plated diamond and tungsten powder. The present invention has no special requirements for the screening and separation process, and the well - known screening process in the art can be used, such as screening with a vibrating screen. The diamond particles after plating of the present invention can be separated from the plating material only by simple screening. The screening is simple, and the product of the plating reaction is tungsten - plated diamond and tungsten powder. The tungsten powder has high commercial value, reducing the plating cost.

[0052] The tungsten - plated diamond obtained by the method of the present invention has a significantly reduced resistivity after tungsten plating compared with the tungsten - plated diamond obtained by the existing tungsten - plating methods due to the continuous coating. Especially for 400 - mesh diamond micropowder, the resistivity drops to 3.4×10 -2 Ω·cm, which can be used for the preparation of precision grinding tools with requirements for diamond conductivity.

[0053] The following combines examples to detail the method for tungsten plating on the diamond surface provided by the present invention, but they cannot be understood as limiting the protection scope of the present invention.

[0054] The preparation method of the colloidal palladium solution used in Examples 1 to 2 is as follows: Add 75 g of stannous chloride to 200 mL of analytical pure hydrochloric acid, stir until completely dissolved, then add 7 g of sodium stannate and stir to make Solution B; Mix 100 mL of analytical pure hydrochloric acid (mass fraction 36 - 38%) with 200 mL of distilled water, stir evenly, then add 1 g of palladium chloride and stir, then add 2.53 g of stannous chloride, stir and allow it to react fully for 10 - 15 min to dissolve, to make Solution A; Slowly add Solution B to Solution A, place the resulting mixture in an aqueous solution at 40 - 50 °C and keep it warm for 3 - 4 h, then add an appropriate amount of deionized water to dilute the solution to 1 L to obtain the colloidal palladium solution.

[0055] Example 1

[0056] Weigh 10.00 g of 40 / 45 mesh synthetic diamond (resistivity 5.4×10 8 Ω·cm) with an analytical balance, place the diamond in 50 mL of 10% NaOH aqueous solution, ultrasonically oscillate and clean for 0.5 h, take it out and wash it with deionized water until neutral; then place the diamond in 50 mL of 10% HCl solution and soak for 0.5 h, take it out and wash it with deionized water until neutral; add 50 mL of 30% nitric acid solution and boil for 10 min for roughening treatment, and wash it with deionized water until neutral to obtain roughened diamond particles; Place the diamond particles in the newly prepared colloidal palladium solution, stir rapidly for 5 min, wash with deionized water until neutral; then use 25 g / L sodium hypophosphite solution to peptize, stir rapidly for 3 min, then wash with deionized water until neutral, then wash with ethanol for 10 min, and finally wash with deionized water until clean. Put the diamond in an oven and dry it at 100 °C for later use to obtain activated diamond particles. Weigh 8.00 g of blue tungsten (particle size 50 nm) with an analytical balance and mix it evenly with the activated diamond particles, transfer it to a porcelain boat, place the porcelain boat in a tubular furnace, heat the temperature to 780 °C under a hydrogen atmosphere and keep it warm for 90 min for the plating reaction; Cool to room temperature with the furnace; Separate the tungsten-plated diamond and the plating material by vibrating sieve to obtain tungsten-plated diamond and W powder. Through analysis and testing, it is found that the coating exists in the forms of WC and W. The resistivity of 40 / 45 mesh tungsten-plated diamond particles is measured to be 0.7 Ω·cm under a pressing pressure of 20 MPa.

[0057] Figure 1 is the SEM image of the diamond after tungsten plating in Example 1, Figure 1 showing that there is no missed plating and no impurity residue in the tungsten-plated diamond prepared by the method of the present invention.

[0058] Figure 2 is the SEM image of the surface coating of the tungsten-plated diamond in Example 1, and it can be seen that the coating is continuous and uniform.

[0059] Figure 3 It is the XRD pattern of tungsten-plated diamond in Example 1. It can be seen from the figure that the coating phase consists of WC and W.

[0060] Example 2

[0061] Weigh 10.00 g of 400-mesh synthetic diamond (resistivity is 1.3×10 8 Ω·cm) with an analytical balance. Place the diamond in 50 mL of 10% NaOH aqueous solution, and ultrasonically oscillate and clean it for 0.5 h. After taking it out, wash it with deionized water until neutral; then place the diamond in 50 mL of 10% HCl solution and soak it for 0.5 h. After taking it out, wash it with deionized water until neutral; add 50 mL of 30% nitric acid solution and boil it for 3 min for roughening treatment, and wash it with deionized water until neutral to obtain roughened diamond particles; place the diamond particles in the newly prepared colloidal palladium solution, stir rapidly for 5 min, and wash it with deionized water until neutral; then use 25 g / L sodium hypophosphite solution to peptize, stir rapidly for 3 min, then wash it with deionized water until neutral, then wash it with alcohol for 10 min, and finally wash it with deionized water. Put the diamond into the oven and dry it at 100 °C for later use to obtain activated diamond particles. Weigh 10.00 g of violet tungsten (particle size is 80 nm) with an analytical balance and mix it evenly with the activated diamond particles, transfer it into a porcelain boat, place the porcelain boat in a tubular furnace, heat the temperature to 760 °C under a hydrogen atmosphere and keep it warm for 90 min for plating reaction; cool it to room temperature with the furnace; separate the tungsten-plated diamond and the plating material by vibrating sieve to obtain tungsten-plated diamond and W powder. Through analysis and testing, it is found that the coating exists in the form of WC and W. It is measured that the resistivity of 400-mesh tungsten-plated diamond particles under a pressing pressure of 20 MPa is 3.4×10 -2 Ω·cm.

[0062] Perform SEM and XRD tests on the tungsten-plated diamond obtained in Example 2. The results are consistent with those in Example 1. SEM shows that there is no missed plating and no impurity residue on the tungsten-plated diamond prepared by the tungsten plating method of the present invention, and the coating is continuous and uniform; the XRD result shows that the coating phase consists of WC and W.

[0063] It can be seen from the above examples that the present invention provides a method for tungsten plating on the surface of diamond, which can form a coating on the surface of diamond at a relatively low temperature to avoid thermal damage to the diamond; the coating is dense and uniform, there is no missed plating phenomenon, and the cost is relatively low.

[0064] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for tungsten plating on the surface of diamond, characterized in that, it includes the following steps: Roughen the diamond particles to obtain roughened diamond particles; the particle size of the diamond particles is 20 - 600 μm; Mix the roughened diamond particles with a colloidal palladium solution for sensitization - activation, and then mix the sensitized - activated diamond particles with a peptizing solution for peptization to obtain activated diamond particles; Mix the activated diamond particles with a plating material, and carry out a plating reaction on the obtained mixture in a hydrogen atmosphere to form a coating on the surface of the diamond; the components of the coating are W and WC; the temperature of the plating reaction is 700 - 800 °C; the plating material is blue tungsten or violet tungsten.

2. The method according to claim 1, characterized in that, the time of the plating reaction is 30 - 180 min.

3. The method according to claim 1, characterized in that, the particle size of the blue tungsten or violet tungsten is 20 - 1000 nm.

4. The method according to claim 1, characterized in that, the mass ratio of the activated diamond particles to the plating material is 1:(0.2 - 2).

5. The method according to claim 1, characterized in that, after completing the plating reaction, it further includes screening and separating the reaction products to obtain tungsten - plated diamond and tungsten powder.

6. The method according to claim 1, characterized in that, the method of roughening is: boil the diamond particles in a nitric acid solution for 3 - 10 min; the mass fraction of the nitric acid solution is 30%.

7. The method according to claim 1, characterized in that, the preparation raw materials of the colloidal palladium solution include: palladium chloride 1 g / L, stannous chloride 77.53 g / L, sodium stannate 7 g / L, hydrochloric acid 300 mL / L and the balance of water; the mass fraction of the hydrochloric acid is 36 - 38%.

8. The method according to claim 1, characterized in that, the time of sensitization - activation is 3 - 6 min.

9. The method according to claim 1, characterized in that, the peptizing solution is dilute hydrochloric acid or sodium hypophosphite solution; the mass fraction of the dilute hydrochloric acid is 10%, and the concentration of the sodium hypophosphite solution is 20 - 30 g / L.

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