Method for plating tungsten on surfaces of diamond particles

Abstract

The invention designs a method for plating metal tungsten on the surfaces of diamond particles by comprehensively utilizing sol-gel and a self-propagating high-temperature synthesis technology, which mainly comprises the following steps of: dissolving a tungsten source in liquid to prepare sol, then adding the diamond particles into the sol, stirring to obtain diamond coated with the sol, and finally, carrying out heat treatment on the diamond coated with the sol. Carrying out calcination and self-propagating high-temperature treatment on the diamond coated with the sol; the ignition temperature of the self-propagating high-temperature treatment is 600-1200 DEG C, a substance used in the self-propagating high-temperature treatment contains a solid reducing agent, the solid reducing agent can reduce non-zero-valent tungsten into zero-valent tungsten, the calcining temperature is greater than 600 DEG C and less than or equal to 700 DEG C, and the calcining time is less than or equal to 5 hours. According to the method, a self-propagating high-temperature rapid reduction method is used for plating the tungsten layer on the diamond for the first time, the plating layer is compact and is well combined with the diamond, and industrial application is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of surface modification, in particular to a method for forming a tungsten film on the surface of diamond particles by using sol-gel and self-propagating high-temperature synthesis technology, and the modified diamond particles can be used to prepare metal matrix composites with diamond particles as reinforcing materials. BACKGROUND

[0002] Due to its high hardness and excellent wear resistance, diamond is the most suitable abrasive for manufacturing hard material machining tools. It has been widely used to manufacture cutting, grinding, polishing and finishing tools. However, due to the small size of diamond particles, diamond tools must be embedded or bonded together with adhesives such as metal, ceramic or resin to achieve efficient machining of workpieces. However, covalently bonded diamond has high interfacial energy, which makes it difficult for the bond to effectively wet the surface of the diamond, the interfacial bonding force is poor, resulting in small holding force on the diamond. When the cutting force is applied, the diamond is easily detached prematurely, reducing the service life and processing efficiency of the diamond tool.

[0003] At present, diamond surface modification is widely used at home and abroad to reduce the interfacial energy between diamond and binder and improve the bonding force between diamond and binder. Diamond surface metallization is to coat a thin film of metal on the surface of diamond or generate a carbide layer by interfacial reaction, so as to improve the chemical affinity between diamond and other metals. The continuous and dense metal plating layer and carbide layer wrap the surface of the diamond, which can not only achieve good interfacial bonding, but also inhibit the thermal damage of the diamond, thereby improving the solderability, sinterability and other properties of the diamond.

[0004] The plating method for diamond surface metallization modification mainly includes chemical plating, electroplating, salt bath plating, CVD, PVD and magnetron sputtering plating, etc. The thickness of the plating layer is nanometer to millimeter, and the plating metal mainly includes Ni, Ti, W, Cr and metal alloy.

[0005] Magnetron sputtering method is a physical vapor deposition method, which is one of the most widely used methods in material surface plating film application due to its simple process and ability to sputter any material at high or low temperature. For example, a layer of tungsten film or molybdenum film can be formed on the surface of diamond by using magnetron sputtering method, which can effectively improve the wettability of diamond and aluminum matrix or copper matrix. However, this method has high requirements for equipment and high plating cost.

[0006] Chemical vapor deposition is one of the commonly used plating methods in industry, which directs the gas containing thin film elements to the substrate, and the gas reacts on the surface of the substrate to form a solid thin film or coating. Compared with physical vapor deposition, it has the advantages of higher plating rate and uniformity of the substrate surface, but the chemical vapor deposition method produces waste gas which needs further treatment, thereby increasing the production cost.

[0007] Sol-gel method is a kind of coating method that substrate material is fully stirred in solution sol to form gel film layer on the surface, and then the film layer is dried by heat treatment. For example, a layer of metal oxide film can be coated on the surface of diamond, SiC particles and the like by using sol, and then the metal oxide on the surface of the reinforcing body particles is reduced to metal element by hydrogen reduction. The process is simple, pollution-free, the obtained film layer is uniform and dense, and can be used for surface coating of materials of various specifications and sizes.

[0008] The commonly used elements for diamond surface metallization include tungsten, molybdenum, chromium, titanium, zirconium and alloys thereof. Among the numerous elements, tungsten has the characteristics of high hardness, good wear resistance, good thermal conductivity and low thermal expansion coefficient, and is one of the preferred elements for diamond surface metallization. After the diamond surface is coated with tungsten, a stable chemical and metallurgical bond is formed between the metal coating and the metal, and the bonding force between the diamond and the metal is greatly enhanced. Therefore, the comprehensive physical properties of the diamond tool are significantly improved. However, the current reduction process for coating tungsten on the surface of diamond requires a very high temperature (such as long-time high-temperature reduction by using gas), which may cause thermal damage to the diamond. Therefore, it is an urgent problem to be solved to reduce the temperature of coating tungsten on the surface of diamond by using appropriate methods. SUMMARY

[0009] Therefore, the purpose of the present application is to provide a method for coating a layer of tungsten on the surface of diamond particles by using sol-gel and self-propagating high-temperature synthesis technology. The present application uses sol-gel and self-propagating high-temperature synthesis technology to modify the surface of diamond particles, and forms a complete and dense tungsten film on the surface of the diamond particles.

[0010] The present application is a method for coating tungsten on the surface of diamond particles, which comprises dissolving tungsten source in a liquid to form sol, then adding diamond particles into the sol and stirring to obtain diamond coated with sol, and then calcining and self-propagating high-temperature treating the diamond coated with sol to obtain diamond coated with tungsten. The ignition temperature of the self-propagating high-temperature treatment is 600-1200℃, and the substance used for the self-propagating high-temperature treatment contains a solid reducing agent which can reduce non-zero valence tungsten to zero valence tungsten. The calcination temperature is greater than 600℃ and less than or equal to 700℃, and the calcination time is less than or equal to 5h.

[0011] As a preferred embodiment, the present application is a method for coating tungsten on the surface of diamond particles, wherein the diamond particles are first subjected to degreasing and then roughening.

[0012] The degreasing process comprises cleaning the diamond particles with 5%-10% alkali solution, stirring at 60-90℃ for 20-40min, and then cleaning and filtering to obtain degreased diamond particles. The alkali is selected from one of potassium hydroxide and sodium hydroxide.

[0013] The roughening is: pouring the defatted diamond particles into a HNO3 solution with a concentration of 20% ~ 30%, continuously stirring at 60℃ ~ 90℃ for 20min ~ 30min, then washing and filtering, and finally drying to obtain the roughened diamond particles.

[0014] As preferred, the method for plating tungsten on the surface of diamond particles, the diamond particles are 200 mesh ~ 230 mesh diamond particles.

[0015] As preferred, the method for plating tungsten on the surface of diamond particles, dissolving the tungsten source in the liquid and preparing the sol includes: dissolving the water-soluble tungsten salt, citric acid and ethylene glycol in deionized water, and continuously stirring the solution at 70℃ ~ 95℃ until a tungsten-containing gel is obtained; the water-soluble tungsten salt is selected from at least one of metatungstate, tungstate and paratungstate.

[0016] As preferred, the method for plating tungsten on the surface of diamond particles, the mass ratio of the water-soluble tungsten salt, citric acid and ethylene glycol is water-soluble tungsten salt: citric acid: ethylene glycol = 8 ~ 12: 2 ~ 6: 1 ~ 5, preferably water-soluble tungsten salt: citric acid: ethylene glycol = 9.5 ~ 10.5: 2.5 ~ 4.5: 1.5 ~ 3.5, which includes water-soluble tungsten salt: citric acid: ethylene glycol = 10: 3: 2.

[0017] After dissolving the water-soluble tungsten salt, citric acid and ethylene glycol in deionized water, the concentration of the water-soluble tungsten salt is 400 ~ 700g / L, preferably 400 ~ 550g / L, and further preferably 450 ~ 550g / L.

[0018] As preferred, the water-soluble tungsten salt is ammonium metatungstate.

[0019] The diamond particles are added to the sol in a mass ratio of diamond particles: water-soluble tungsten salt = 1: 1.5 ~ 4, preferably 1.5 ~ 2.5: 1, and stirred to obtain the diamond coated with the sol. Controlling the mass ratio of the diamond particles and the water-soluble tungsten salt and the mass ratio of the water-soluble tungsten salt, citric acid and ethylene glycol is a prerequisite for ensuring that W is as uniformly coated on the diamond particles as possible, which provides a necessary condition for obtaining a uniform W layer as much as possible later.

[0020] As preferred, the method for plating tungsten on the surface of diamond particles, the diamond coated with the sol is dried at 120 ~ 160℃ for 8h ~ 15h before calcination.

[0021] As preferred, the method for plating tungsten on the surface of diamond particles, the temperature of the calcination is 600℃ ~ 700℃, and the time is 2h ~ 5h.

[0022] As preferred, the method for plating tungsten on the surface of diamond particles in the present application, after the calcined diamond particles are mixed with the reducing agent uniformly, ignition and self-propagating high-temperature treatment are carried out at 600-1200℃, preferably 600-1000℃, and further preferably 900-1000℃.

[0023] As preferred, the method for plating tungsten on the surface of diamond particles in the present application, after the calcined diamond particles are mixed with magnesium powder and sodium chloride uniformly, ignition is carried out in a sintering furnace, and after the combustion is completed, heating is maintained for 0-60 min, to obtain diamond particles wrapped with a tungsten film on the surface. The amount of magnesium powder is 1.05-1.12 times, preferably 1.095-1.105 times, the theoretical amount, and the mass of sodium chloride accounts for 10%-60%, preferably 30-40%, and further preferably 34-36%, of the total mass of the powders used, including the calcined diamond particles, magnesium powder and sodium chloride. In the present application, the theoretical amount refers to the amount of reducing the tungsten source to elemental tungsten with magnesium as the reducing agent. In the present application, the amount of magnesium powder must be controlled. If the amount exceeds the standard and no sodium chloride is added, the implementation of the entire scheme becomes uncontrollable, and the integrity of the W film obtained is extremely poor. After selecting an appropriate amount of magnesium powder, an appropriate amount of sodium chloride must be added, otherwise it may directly lead to experimental failure.

[0024] As preferred, the method for plating tungsten on the surface of diamond particles in the present application, after the product obtained by self-propagating high-temperature treatment is cleaned with hydrochloric acid at 30-90℃ for 10-40 min, stirring, and then stirred with NaOH solution at 30-90℃ for 10-40 min, solid-liquid separation is carried out, and finally the solid is dried, to obtain tungsten-plated diamond.

[0025] As preferred, in the present application, the product obtained by self-propagating high-temperature treatment is treated with 50% mass percent hydrochloric acid. Of course, other concentrations of hydrochloric acid can also be used in the present application. After pickling, the mass percent concentration of sodium hydroxide used for alkali washing is 2%-10%.

[0026] The present application modifies the surface of diamond particles. In order to make the metal film layer on the surface of diamond particles complete and dense, the present application uses sol-gel method and self-propagating high-temperature synthesis method to form a layer of tungsten film on the surface of diamond particles; in order to improve the plating efficiency of the film layer, the raw diamond particles are cleaned and roughened before sol coating; further, after the diamond particles are coated with sol, dried and calcined at high temperature, the tungsten oxide layer on the surface of the diamond particles is reduced by self-propagating high-temperature synthesis method.

[0027] The method for plating tungsten film on the surface of diamond particles by using sol-gel method and self-propagating high-temperature synthesis method in the application removes oil stains and metal ions on the surface of diamond particles by degreasing and roughening the raw diamond particles before coating the surface of the diamond particles with sol, thereby improving plating efficiency; the diamond particles are coated with sol and dried, and then calcined at a proper temperature to form a tungsten oxide layer on the surface of the diamond particles; then the tungsten oxide on the surface of the diamond particles is reduced by using self-propagating high-temperature synthesis method, and finally the tungsten-plated diamond is obtained through impurity removal treatment.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] (1) The surface of the diamond particles after degreasing and roughening is coated with prepared ammonium metatungstate sol, dried, and calcined to form a tungsten oxide layer on the surface of the diamond particles; the dried diamond powder is reduced by using magnesium powder self-propagating high-temperature synthesis method to quickly form a complete and dense metal tungsten film layer structure on the surface of the diamond particles. The plating process of the application has good repeatability and can be used to improve the interface bonding performance of metal matrix composites.

[0030] (2) The raw materials used are simple and convenient to obtain, and the preparation raw materials of the ammonium metatungstate sol mainly include ammonium metatungstate, citric acid and ethylene glycol, and no toxic gas is generated in the reaction, which is harmless to human body.

[0031] (3) The sol-gel method used in the application has high raw material utilization rate, no by-products are generated in the sol preparation process, no pollution to the environment, and the process cost is saved.

[0032] (4) The self-propagating high-temperature synthesis method for reducing tungsten oxide is fast and has small thermal damage to the surface of the diamond. The W layer coated on the diamond is prepared by using the self-propagating high-temperature rapid reduction synthesis method for the first time, and the rapid thickening of the W layer is realized by controlling the short holding time after the self-propagating high-temperature reaction.

[0033] In order to better understand and implement, the application will be described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The micro-morphology (BSEM) of the tungsten-plated diamond of Example 1 of the application;

[0035] Figure 2 The XRD spectrum and phase analysis results of the tungsten-plated diamond of Example 1 of the application.

[0036] Figure 3 The electron microscope graph of the tungsten-plated diamond obtained in Example 1 of the application.

[0037] Figure 4Micro-morphology (BSEM) of the tungsten-plated diamond of the present application example 2;

[0038] Figure 5 XRD pattern and phase analysis result of the tungsten-plated diamond of the present application example 2.

[0039] Figure 6 Electron microscope graph of the tungsten-plated diamond of the present application example 2.

[0040] Figure 7 Micro-morphology (BSEM) of the tungsten-plated diamond of the present application exploration case;

[0041] Figure 8 XRD pattern and phase analysis result of the tungsten-plated diamond of the present application exploration case. DETAILED DESCRIPTION

[0042] In order to further understand the present application, the following embodiments are combined to provide a detailed description of the process of plating a metal tungsten film on the surface of diamond particles by using a sol-gel method and a self-propagating high-temperature synthesis method. The protection scope of the present application is not limited by the following specific embodiments.

[0043] Example 1

[0044] The specific steps of plating a metal tungsten film on the surface of diamond particles by using a sol-gel method are as follows:

[0045] S1: Surface degreasing and roughening of diamond particles: 30g of 200-230 mesh diamond particles are washed with 5% KOH, stirred at 70℃ for 30min, then washed and filtered to obtain degreased diamond particles; the degreased diamond particles are poured into a 20% HNO3 solution, heated and stirred, and continuously stirred at 70℃ for 30min, then washed, filtered and roughened.

[0046] In S2, the preparation method of the ammonium metatungstate sol includes the following steps: according to the mass of ammonium metatungstate, citric acid and ethylene glycol being 10g, 3g and 2g respectively, ammonium metatungstate, citric acid and ethylene glycol are sequentially dissolved in 20ml deionized water, and the solution is continuously stirred at 80℃ until ammonium metatungstate gel is obtained.

[0047] In S3, the method for coating and drying the surface of diamond particles includes the following steps: the ammonium metatungstate sol prepared in S2 is heated and concentrated at 80℃, after the solution becomes gelatinous, it is poured into the diamond particles treated in S1, stirred for 10-20min, then filtered and dried, the drying temperature is 150℃, the drying time is 8h, finally the diamond powder wrapped with a layer of ammonium metatungstate gel film on the surface is obtained, i.e. the diamond particles treated in S3.

[0048] In S4, the diamond particles treated in S3 are put into a muffle furnace, the calcination temperature is 600℃, and the calcination time is 5h. The ammonium paratungstate on the surface of the diamond is decomposed into WO3, and diamond particles coated with a layer of WO3 film are obtained, i.e., the calcined powder after S4 treatment.

[0049] In S5, 7.7g of the diamond particles after S4 treatment are mixed with excess 10% magnesium powder and 3.35g of sodium chloride uniformly (at this time, the sodium chloride accounts for 35% of the total mass of the diamond + magnesium powder + sodium chloride), ignited at 950℃ in a super-fast sintering furnace, and kept heating for 10min after the combustion is completed, to obtain diamond particles coated with a layer of tungsten film, i.e., the diamond particles after S5 treatment.

[0050] In S6, after the diamond particles after S5 treatment are cleaned with dilute hydrochloric acid at 50℃ for 40min, and then treated with 3% NaOH solution at 70℃ for 40min to remove excess impurities, and finally dried, tungsten-coated diamond is obtained.

[0051] S7: Microstructure analysis and phase analysis: the microstructure of the tungsten-coated diamond and the integrity of the surface film layer are observed by SEM (see Figure 1 ), and the phase analysis of the composite powder is performed by XRD (see Figure 2 ), from Figure 3 which it can be further seen that the obtained W layer is relatively complete, and the thickness of the tungsten layer is also relatively thick.

[0052] Through detection, the tungsten-coated diamond obtained by the plating process has a complete film layer structure on the surface of the diamond particles. The XRD analysis shows that the composite powder contains diamond, tungsten, and tungsten carbide phases.

[0053] Example 2:

[0054] In this example, a sol-gel method is used to coat a tungsten film on the surface of the diamond particles, and the specific steps are as follows:

[0055] S1, S2, S3, and S4 are consistent with Example 1.

[0056] In S5, 7.7g of the diamond particles after S4 treatment are mixed with excess 10% magnesium powder and 3.35g of sodium chloride uniformly, at this time, the sodium chloride accounts for 35% of the total mass of the diamond + magnesium powder + sodium chloride, ignited at 950℃ in a super-fast sintering furnace without holding, to obtain diamond particles, i.e., the diamond particles after S5 treatment.

[0057] In S6, after the diamond particles after S5 treatment are cleaned with dilute hydrochloric acid at 50℃ for 40min, and then treated with 3% NaOH solution at 70℃ for 40min to remove excess impurities, and finally dried, tungsten-coated diamond is obtained.

[0058] S7: Microstructure analysis and phase analysis: SEM was used to observe the micro-morphology of the tungsten-coated diamond and the integrity of the surface film layer (attached Figure 4 ), and XRD was used to analyze the phase of the composite powder (attached Figure 5 ).

[0059] From Figure 4 , Figure 5 it can be seen that only a few diamonds in Example 2 are coated with a small amount of tungsten. From Figure 6 it can be further seen that the obtained W layer is not complete, and the thickness of the tungsten layer is thin.

[0060] From Examples 1 and 2, it can be seen that the coating completeness of the W layer in the product obtained in Example 1 is much better than that in Example 2. At the same time, the content of W in the product obtained in Example 1 is also much higher than that in Example 2.

[0061] Exploration case

[0062] In this case, a sol-gel method is used to coat a tungsten film on the surface of diamond particles, and the specific steps are as follows:

[0063] S1, S2, S3, and S4 are consistent with Example 1;

[0064] In S5, 7.7g of diamond particles treated in S4 are mixed with excess 10% magnesium powder and 6.7g of sodium chloride, and the sodium chloride accounts for 71% of the total mass of diamond + magnesium powder + sodium chloride at this time. Ignite at 950℃ in a super-fast sintering furnace without holding, and the obtained diamond particles, i.e. diamond particles treated in S5.

[0065] In S6, after the diamond particles treated in S5 are cleaned with dilute hydrochloric acid at 50℃ for 40min and then treated with 3% NaOH solution at 70℃ for 40min, the excess impurities are removed, and finally dried, the tungsten-coated diamond is obtained.

[0066] S7: Microstructure analysis and phase analysis: SEM was used to observe the micro-morphology of the tungsten-coated diamond and the integrity of the surface film layer (attached Figure 7 ), and XRD was used to analyze the phase of the composite powder (attached Figure 8 ).

[0067] From Figure 7 , Figure 8 it can be seen that the diamond surface in the exploration case is not coated with a tungsten layer.

[0068] The above described embodiments only express one embodiment of the present application, which is described in more detail and in more detail, but cannot be understood as limiting the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, and the present application also intends to include these modifications and improvements.

Claims

1. A method of plating tungsten on the surface of diamond particles, characterized by: The tungsten source is dissolved in a liquid to form a sol, and then the diamond particles are added to the sol and stirred to obtain the sol-coated diamond, and the sol-coated diamond is calcined and subjected to self-propagating high-temperature treatment; the tungsten-coated diamond is obtained, the ignition temperature of the self-propagating high-temperature treatment is 600-1200℃, the substance used for the self-propagating high-temperature treatment contains a solid reducing agent, the solid reducing agent can reduce the non-zero-valent tungsten to zero-valent tungsten, the calcination temperature is greater than 600℃ and less than or equal to 700℃, and the calcination time is less than or equal to 5h.

2. A method of coating diamond particles with tungsten as claimed in claim 1, wherein: The diamond particles are diamond particles subjected to degreasing and roughening; The degreasing is: using 5%-10% alkali solution to clean the diamond particles, stirring at 60-90℃ for 20-40min, and then cleaning and filtering to obtain the degreased diamond particles; the alkali is selected from one of potassium hydroxide and sodium hydroxide; The roughening is: pouring the degreased diamond particles into a HNO3 solution with a concentration of 20%-30%, continuously stirring at 60-90℃ for 20-30min, cleaning and filtering, and finally drying to obtain the roughened diamond particles.

3. A method of coating a diamond particle with tungsten as claimed in claim 1, wherein: The diamond particles are 200-230 mesh diamond particles.

4. The method of claim 1, wherein: The dissolving of the water-soluble tungsten salt, citric acid and ethylene glycol in deionized water and the continuous stirring of the solution at 70-95℃ until a tungsten-containing gel is obtained; the water-soluble tungsten salt is selected from at least one of metatungstate, tungstate and paratungstate.

5. The method of claim 1, wherein: The mass ratio of the water-soluble tungsten salt, citric acid and ethylene glycol is: water-soluble tungsten salt: citric acid: ethylene glycol = 8-12: 2-6: 1-5, preferably water-soluble tungsten salt: citric acid: ethylene glycol = 9.5-10.5: 2.5-4.5: 1.5-3.5, which includes water-soluble tungsten salt: Citric acid: ethylene glycol = 10: 3: 2; After the water-soluble tungsten salt, citric acid and ethylene glycol are dissolved in deionized water, the concentration of the water-soluble tungsten salt is 400-700g / L, preferably 400-550g / L, and further preferably 450-550g / L.

6. The method of claim 1, wherein: The diamond particles are added to the sol in a mass ratio of diamond particles: water-soluble tungsten salt = 1: 1.5-4, preferably 1.5-2.5: 1, and stirred to obtain the sol-coated diamond.

7. A method of coating diamond particles with tungsten as claimed in claim 1, wherein: The sol-coated diamond is dried at 120-160℃ for 8-15h before calcination; The calcination temperature is 600-700℃, and the time is 2-5h.

8. The method of claim 1, wherein: The calcined diamond particles are mixed uniformly with the reducing agent, ignited at 600-1200℃, preferably 600-1000℃, and further preferably 900-1000℃, and subjected to self-propagating high-temperature treatment.

9. A method of coating a diamond particle with tungsten as claimed in claim 8, wherein: The calcined diamond particles are mixed with magnesium powder and sodium chloride uniformly, ignited in a sintering furnace, and heated for 0-60 min after the combustion is completed to obtain diamond particles coated with a layer of tungsten film on the surface; the amount of magnesium powder is 1.05-1.12 times, preferably 1.095-1.105 times of the theoretical amount, the mass of sodium chloride accounts for 10%-60%, preferably 30-40%, further preferably 34-36% of the total mass of the powders used, and the powders used include the calcined diamond particles, magnesium powder and sodium chloride.

10. A method of coating a diamond particle with tungsten as claimed in claim 8, wherein: The product obtained by the self-propagating high-temperature process is cleaned by stirring in hydrochloric acid at 30-90 ℃ for 10-40 min, then stirred in NaOH solution at 30-90 ℃ for 10-40 min, solid-liquid separation, and finally drying the solid to obtain tungsten-coated diamond.

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