A method for preparing a metal coated abrasive having a surface with oscillation assisted hydrolysis

Abstract

The application relates to a method for preparing abrasives with metal coating on the surface by using oscillation-assisted hydrolysis, and belongs to the technical field of abrasive surface coating preparation. The method comprises the following steps: weighing abrasives, cleaning the abrasives to neutral after oil removal treatment; adding an inorganic metal salt solution, uniformly stirring, placing in a water bath tank for constant temperature water bath heating, keeping warm and continuously stirring; stopping heating after oscillation treatment, taking out the abrasives with metal oxide formed on the surface, cleaning the abrasives with pure water, placing the abrasives in a reducing agent solution for reduction, cleaning, drying, and then obtaining the abrasives with metal coating on the surface. The metal coating obtained by the method has high activity, strong binding force, controllable thickness and uniformity, is especially suitable for subsequent chemical plating, electroplating and other process links or direct use, and has great application potential in the fields of silicon wafer cutting, wafer grinding and polishing and fine processing.

Description

Technical Field

[0001] This invention belongs to the field of abrasive surface coating preparation technology, and specifically relates to a novel preparation method for obtaining abrasive surface metal coating by vibration-assisted hydrolysis. Background Technology

[0002] Hard abrasives are widely used in industry due to their grinding performance, especially in grinding wheels and cutting tools for fine grinding, polishing, and cutting of parts. Currently, industrially available abrasives include diamond, alumina, silicon carbide, boron carbide, and cubic boron nitride. Because most abrasives have high interfacial energy with the metals and ceramics used in grinding tools, poor wettability and bonding strength between them and the matrix lead to abrasive detachment. Furthermore, the high-temperature pressing process typically used in grinding tool manufacturing causes oxidation of the abrasive, significantly affecting its performance.

[0003] To reduce the interfacial energy between the abrasive and the substrate, improve wettability, and prevent high-temperature oxidation or graphitization of the abrasive, metallization of the abrasive surface is employed to address these issues. Traditional methods for obtaining abrasive surface coatings include: electroless plating, electroplating, physical vapor deposition, chemical vapor deposition, magnetron sputtering, vacuum micro-evaporation plating, powder coating sintering, and salt bath plating. However, these traditional methods are costly, technically complex, and cause significant pollution, hindering the further development of the abrasive industry.

[0004] This invention is based on the theory of solution hydrolysis. When a metal salt solution dissolves in distilled water, it hydrolyzes in the solution to form corresponding hydrated metal oxides and metal hydroxides. The constant-temperature water bath step promotes this process and allows the hydrolysis acid products to volatilize and be discharged. The formed hydrated metal oxides and hydroxides are adsorbed onto the surface of the dispersed abrasive powder and, after reduction, yield a uniform metal coating. Ultrasonic vibration disperses the hydrolysis products in the solution, further increasing the nucleation sites and promoting the reaction. It also provides homogenization and prevents the abrasive powder from agglomerating.

[0005] The abrasive surface coating prepared by the oscillation-assisted hydrolysis method is low in cost and simple in technology. The quality of the coating is controllable and it is conducive to subsequent composite coating by other means. It effectively makes up for the technical shortcomings of traditional coating methods, lowers the technical threshold of abrasive preparation, and will greatly promote the development of semiconductor manufacturing, industrial production, photovoltaic materials and other fields. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to design and provide a novel method for preparing abrasive surface coatings that is simple to operate, low in cost, and produces excellent coating results. This invention utilizes an inorganic metal salt solution mixed with abrasive particles. The salt solution undergoes thermal hydrolysis and agitation to assist nucleation and growth on the abrasive surface. After a reduction operation, the corresponding surface metal coating is obtained.

[0007] This invention employs a vibration-assisted hydrolysis method to generate a surface metallic coating. The effects of the water bath and vibration are as follows:

[0008] M salt + H₂O → M(OH)n + acid

[0009] M(OH)n→MOn+H2O

[0010] Metal salts are dissolved in distilled water, and ultrasonic vibration assists in a slow, non-boiling hydrolysis to generate hydroxides and acids. The acid volatilizes and overflows during heating. Vibration causes the formed hydroxides to adsorb onto the uniformly dispersed abrasive surface, agglomerating to form an oxide coating. The oxide coating is subsequently reduced to the corresponding metal in a reducing agent. This step eliminates the need for acid washing pretreatment of the abrasive, avoiding the introduction of excess functional groups and active surface defects. Another benefit of vibration is ensuring the uniformity of oxide distribution within the abrasive, rather than the formation of clusters and agglomerates.

[0011] Ultrasonic oscillation promotes further destabilization and decomposition of the solution, while also increasing the opportunity for hydrolysis products to come into contact with the abrasive. Ultrasonic stimulation and a non-boiling water bath allow the hydrolysis products to fully contact the abrasive surface for nucleation and growth, forming a coating, rather than simply being dispersed in the solution. In traditional techniques, the coating originates from oxides already present in the solution, formed by immersing the abrasive and then attaching the metal oxide. This is unlike the in-situ nucleation and growth process used in this technology, resulting in lower loading capacity and poorer holding power.

[0012] The thickness of the coating varies with the reaction time; the longer the holding time is within the specified range, the greater the weight gain of the coating. This is because crystals continuously grow after nucleation on the abrasive surface. The morphology of the coating is controlled by the heating method; microwave oscillation can produce spherical metal coatings, while water bath heating can produce strip-shaped metal coatings.

[0013] Inorganic non-metallic surfaces are extremely difficult to initiate autocatalytic redox reactions (chemical plating), and they are also non-conductive, making electroplating impossible. Traditional techniques for depositing metallic coatings onto inorganic materials require active metal targets to initiate the chemical or electroplating reaction. Taking diamond as an example, due to its high surface energy and strong chemical inertness, CVD / PVD methods involve complex equipment, high power consumption, and difficulty in uniformly depositing abrasive microparticles because vapor deposition involves a unidirectional contact surface. Furthermore, preparing metallic coatings via solution methods requires creating active metal targets on the surface, which in traditional techniques involves multiple steps and high costs. Our proposed method aims to easily and cost-effectively form spot-like metallic coatings on abrasive surfaces, which can be used directly as a single coating or further chemically or electroplated to create composite coatings.

[0014] To achieve the above objectives, the present invention adopts the following technical solution:

[0015] A method for preparing an abrasive with a metal coating on its surface, characterized by comprising the following steps:

[0016] (1) Weigh the abrasive, degrease it and clean it until it is neutral;

[0017] (2) Add the abrasive treated in step (1) to the inorganic metal salt solution, stir evenly, place it in a water bath and heat it to 80℃~100℃, keep it at the temperature for 1h~8h, and stir continuously.

[0018] Alternatively, (2') add the abrasive treated in step (1) to an inorganic metal salt solution, stir evenly, place it in a water bath and heat it at a constant temperature of 60-80°C for 30 min-1 h, while adding 3% ammonia or 1% sodium hydroxide and stirring continuously; (3) after shaking treatment, stop heating when the solution is flocculent and milky white, take out the abrasive with metal oxide formed on the surface and wash it with pure water, put it in a reducing agent solution for reduction, wash and dry to obtain the abrasive with a metal coating on the surface.

[0019] In the preparation method described above, the abrasive is one or more of silicon carbide, boron carbide, cubic boron nitride, diamond, and alumina; the abrasive is one or more of micro powder, particles, whiskers, or fibers; and the surface of the abrasive is smooth or has been coated with a metal coating.

[0020] In the preparation method described above, the metal coating is one or more of titanium, chromium, and tungsten, the particle size of the micro powder is 0.1 μm to 40 μm, and the size of the particles is 20 mesh to 400 mesh.

[0021] In the preparation method described above, the mass-to-volume ratio of the abrasive, the inorganic metal salt solution in step (2) or the inorganic metal salt solution and the reducing agent solution in step (2') is 5-20g:100mL:50mL.

[0022] The mass-to-volume ratio of the abrasive to 3% ammonia or 1% sodium hydroxide in step (2') is 5–20 g: 10–40 mL.

[0023] In the preparation method described above, the inorganic metal salt solution is one or more of nickel salt or its derivatives, copper salt or its derivatives, iron salt or its derivatives, and cobalt salt or its derivatives; the concentration of the inorganic metal salt solution is 2% to 20%.

[0024] In the preparation method described above, the concentration of the inorganic metal salt solution is 5% to 10%.

[0025] In the preparation method described above, the reducing agent is one or more of sodium borohydride or sodium hypophosphite.

[0026] The preparation method described herein includes one or more of stirring, ultrasonic oscillation, magnetic stirring, and microwave oscillation, with the oscillation time being 3 to 10 minutes.

[0027] In the preparation method described above, the heating temperature in step (2) is 90°C and the holding time is 1 hour.

[0028] The preparation method described herein is applied in the preparation of abrasives with a metal coating on the surface.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The raw materials of this invention are readily available, the equipment is simple, the operation is easy, the cost is low and the environment is environmentally friendly, and it is easy to process and scale up production.

[0031] 2. The present invention uses in-situ nucleation growth in the preparation process, the coating condition is controllable and the dispersion is excellent, and the reaction time is controllable and rapid.

[0032] 3. The metal coating obtained by the method of the present invention has strong activity and is suitable for flexible adjustment under different usage conditions. It can continue to undergo secondary plating processes such as chemical plating and electroplating, replacing the existing plating activation methods.

[0033] 4. The metal coating obtained by this invention is adaptable to various coating substrates and particle sizes, and can be applied to fields such as abrasive manufacturing and silicon wafer cutting wire saws.

[0034] 5. This invention can also use pre-coated metal abrasives (such as titanium-plated or chromium-plated abrasives) to perform the experimental steps in this invention. This solves the problem of existing technologies using pre-coated diamonds (such as titanium-plated diamonds) for electroless nickel plating, which requires multiple processes and cleaning steps (sensitization-activation, etc.), and consumes the precious metal palladium. Following this technique eliminates these steps, allowing direct plating to obtain a speckled nickel coating. Achieving the final effect of this technology is easier and results in a greater coating weight gain. Attached Figure Description

[0035] Figure 1 The images show the analysis of diamond powder containing nickel on its surface in Example 1, where a is a SEM image of a single nickel layer prepared on the surface of diamond powder by oscillation-assisted hydrolysis (a); b is the EDS energy dispersive spectroscopy results and elemental content.

[0036] Figure 2 Structural diagrams of nickel-coated diamond and nickel-plated diamond obtained by electroless nickel plating of diamond, wherein (a) is nickel-coated diamond obtained by vibration-assisted hydrolysis; and (b) is nickel-plated diamond obtained by electroless nickel plating of diamond in (a).

[0037] Figure 3 The image shows the analysis of chromium-plated diamond powder with a composite coating of iron, cobalt, and nickel on the surface in Example 4. In the image, a is a SEM image of various metal coatings prepared on the surface of chromium-plated diamond by oscillation-assisted hydrolysis; b is the EDS energy dispersive spectroscopy results and elemental content.

[0038] Figure 4 The diagram shows the structure of an uncoated diamond wire saw and a diamond wire saw with a composite metal coating. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] Example 1:

[0041] 5g of diamond powder with an average particle size of 8 micrometers was weighed and treated with a 2% degreasing agent solution until neutral. 100mL of a 6% nickel sulfate solution was added and stirred until homogeneous. The mixture was then placed in a 90℃ water bath and heated continuously with stirring. After 1 hour, it was removed and placed in an ultrasonic cleaner and agitated for 3 minutes. Heating was stopped when the solution turned a flocculent milky white. The diamond powder was then removed and washed 4-5 times with pure water, then reduced in a sodium hypophosphite solution. After washing and drying, a diamond abrasive with a nickel coating was obtained. Figure 1 This is an analytical diagram of diamond powder containing nickel on its surface.

[0042] The diamond abrasive obtained by the above method can be electroless nickel plated, which can successfully and rapidly induce a reaction, thereby obtaining a complete electroless nickel plating coating. For example... Figure 2 Structure diagrams of nickel-coated diamond and nickel-plated diamond obtained by electroless nickel plating of diamond.

[0043] Example 2:

[0044] 5g of silicon carbide micropowder with an average particle size of 40 micrometers was weighed, degreased with a 2% degreasing agent solution, and washed until neutral. 100mL of a 3% ferric chloride solution was added and stirred until homogeneous. The mixture was then placed in a 90℃ water bath for constant heating. Every 20 minutes, the mixture was removed and placed in an ultrasonic cleaner for 1 minute of agitation, followed by stirring and continued in the water bath for heat preservation. After 10 cycles, heating was stopped when the solution reached a flocculent colloidal state. The silicon carbide was then removed and washed 4-5 times with pure water, reduced in a sodium hypophosphite solution, and subsequently washed and dried to obtain silicon carbide abrasive with an iron coating on the surface.

[0045] The silicon carbide abrasive obtained by the above method was mixed with a metal binder at a ratio of 15 wt.% to 85 wt.%, and the resulting grinding wheel was obtained by spark plasma sintering. This mixture was then used to grind CVD diamond films, achieving a removal rate more than 8 times higher than that of uncoated silicon carbide grinding wheels. The bonding strength between the coated silicon carbide and the binder was approximately 220 MPa higher than that of uncoated silicon carbide grinding wheels.

[0046] Example 3:

[0047] 5g of boron carbide micropowder with an average particle size of 5 micrometers was weighed and treated with a 2% degreasing agent solution until neutral. After centrifugation, 100mL of a 10% cobalt chloride solution was added and stirred until homogeneous. Then, the mixture was continuously stirred at 80℃ and 600r / min for 1 hour in a magnetic stirring and heating device until a semi-transparent colloid was formed. The boron carbide was allowed to stand to separate, washed 4-5 times with pure water, and then reduced in a sodium hypophosphite solution. After separation, washing, and drying, boron carbide abrasive with a cobalt coating on the surface was obtained.

[0048] Example 4:

[0049] Chromium-plated diamond abrasive with a total concentration of 10% (nickel sulfate, ferrous sulfate, and cobalt sulfate) and an average particle size of 8 micrometers was prepared. 10g of chromium-plated diamond powder with an average particle size of 8 micrometers was weighed, degreased with a 2% degreasing agent solution, and washed until neutral. 100mL of a 10% mixed solution of nickel sulfate, ferrous sulfate, and cobalt sulfate was added and stirred until homogeneous. The mixture was then placed in an 80℃ water bath and heated for 30 minutes, followed by ultrasonic cleaning for 1 minute. Then, 3mL of ammonia solution was added and stirred until homogeneous. The mixture was then heated in a microwave oven for 1 minute until the solution became a flocculent colloid. After standing, the chromium-plated diamond was separated and washed 4-5 times with pure water. It was then reduced in a sodium hypophosphite solution, followed by washing and drying to obtain chromium-plated diamond with a nickel, cobalt, and iron composite coating. Figure 3 This is an analytical diagram of chromium-plated diamond powder with a composite coating of iron, cobalt, and nickel on its surface.

[0050] Using diamond with the aforementioned metal-coated diamond to prepare diamond wire saws, the abrasive density on the wire saw was more than doubled compared to the uncoated wire saw during the composite electroplating (i.e., abrasive coating) process. The results are as follows: Figure 4 .

Claims

1. A method for preparing an abrasive with a metal coating on its surface, characterized in that, Includes the following steps: (1) Weigh the abrasive, degrease it and clean it until it is neutral; (2) Add the abrasive treated in step (1) to the inorganic metal salt solution, stir evenly, place it in a water bath and heat it to 80℃~100℃, keep it at the temperature for 1h~8h, and stir continuously. Alternatively, (2') add the abrasive treated in step (1) to an inorganic metal salt solution, stir evenly, place it in a water bath and heat it at a constant temperature of 60~80℃ for 30min~1h, while adding 3% ammonia or 1% sodium hydroxide and stirring continuously. (3) After shaking treatment, when the solution is flocculent and milky white, stop heating, take out the abrasive with metal oxide formed on the surface and wash it with pure water, put it in the reducing agent solution for reduction, wash and dry to obtain the abrasive with metal coating on the surface; The inorganic metal salt solution is one or more of nickel salt or its derivatives, copper salt or its derivatives, iron salt or its derivatives, and cobalt salt or its derivatives; the concentration of the inorganic metal salt solution is 2% to 20%.

2. The preparation method according to claim 1, characterized in that, The abrasive is one or more of silicon carbide, boron carbide, cubic boron nitride, diamond, and alumina; the abrasive is one or more of micro powder, granules, whiskers, or fibers; the surface of the abrasive is smooth or has been coated with a metal coating.

3. The preparation method according to claim 2, characterized in that, The metal coating is one or more of titanium, chromium, and tungsten, the micro powder has a particle size of 0.1μm to 40μm, and the particle size is 20 mesh to 400 mesh.

4. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of the abrasive, the inorganic metal salt solution in step (2) or the inorganic metal salt solution and reducing agent solution in step (2') is 5~20g:100mL:50mL; The mass-to-volume ratio of the abrasive to 3% ammonia or 1% sodium hydroxide in step (2') is 5~20g:10~40mL.

5. The preparation method according to claim 1, characterized in that, The concentration of the inorganic metal salt solution is 5% to 10%.

6. The preparation method according to claim 1, characterized in that, The reducing agent is one or more of sodium borohydride or sodium hypophosphite.

7. The preparation method according to claim 1, characterized in that, The vibration treatment includes one or more of stirring, ultrasonic vibration, magnetic stirring, and microwave vibration, and the vibration time is 3 to 10 minutes.

8. The preparation method according to claim 1, characterized in that, The heating temperature in step (2) is 90°C, and the holding time is 1 hour.

9. The application of the preparation method according to any one of claims 1-8 in the preparation of abrasives with a metal coating on the surface.

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