Hollow agglomerated diamond microspheres, diamond grinding tool and application

Abstract

The invention provides a hollow agglomerated diamond microsphere, a diamond grinding tool and application. According to the hollow agglomerated diamond microspheres, a first ceramic bond and diamond micro-powder are mainly used as raw materials, alkoxide is used as a binder, water is used as a solvent, and evenly-mixed ceramic slurry is prepared; performing granulation treatment on the ceramic slurry by adopting a centrifugal spray granulation method to prepare a hollow agglomerated diamond microsphere blank; and carrying out high-temperature calcination treatment on the hollow agglomerated diamond microsphere blank to obtain the hollow agglomerated diamond microsphere. The alkoxide is used as the binder, so that the hollow agglomerated diamond microspheres can be prevented from being sunken due to low bonding strength of organic matters, and the preparation of the high-sphericity agglomerated diamond hollow spheres can be realized. The hollow agglomerated diamond microspheres serve as a pore forming agent and abrasive particles, the problem that pores in a diamond grinding wheel are not evenly distributed can be solved, and the sharpness and self-sharpening performance of a grinding tool are improved.

Description

Technical Field

[0001] This invention relates to the field of superhard materials, specifically to a hollow aggregated diamond microsphere, a diamond abrasive, and its applications. Background Technology

[0002] Ceramic-bonded diamond grinding wheels, due to the strong chemical stability, high hardness, and high-temperature resistance of the ceramic bond, and its strong bond with diamond abrasive grains, meet the requirements of high-speed and high-pressure environments and are widely used in the precision machining of hard and brittle materials, such as silicon wafers, silicon carbide (SiC), sapphire substrates, optical glass and crystals, precision ceramics, and cemented carbides. The pores in ceramic-bonded diamond grinding wheels serve as chip removal channels, chip-holding spaces, and enhance cooling and heat dissipation, which are key features distinguishing them from other bonded grinding wheels and play a crucial role in grinding performance and machining results. Furthermore, the porous structure can promote wheel self-sharpening by regulating abrasive grain shedding and homogenizing the load, thus maintaining grinding performance. Ceramic-bonded diamond grinding wheels have significant advantages in the field of precision grinding due to their unique material properties and structural design. By adjusting the porosity, pore size, and distribution, wheel weight can be achieved, and wheel vibration can be suppressed, improving machining stability and enabling them to meet the requirements of rough grinding, fine grinding, and ultra-fine grinding.

[0003] Currently, methods for controlling porosity mainly include adding volatile / decomposable organic pore-forming agents, such as starch, graphite, and polyvinyl alcohol; adding inorganic pore-forming agents, such as carbonates, sulfates, and hollow ceramic spheres (glass, alumina, silicon carbide, etc.); adjusting the composition and ratio of the binder, such as introducing porous fillers (porous alumina, diatomaceous earth), and controlling the ratio of abrasive to binder; and adjusting the preparation process, such as controlling the pressing pressure and firing temperature. Currently, the decomposition temperature range of organic pore-forming agents is relatively narrow. In the preparation of porous ceramic binder grinding wheels, the sintering temperature does not match that of the ceramic binder. At low temperatures, volatilization causes a decrease in the strength of the green body, making it prone to deformation and cracking. At high temperatures, residual carbides damage the chemical stability of the binder and reduce the wear resistance of the grinding wheel. Although organic pore-forming agents can avoid some of the defects of organic materials, they still have problems such as a narrow porosity adjustment range and low reactivity with the binder. Adding inorganic pore-forming agents such as alumina and hollow glass microspheres to ceramic-bonded diamond grinding wheels can effectively regulate the pore structure and improve some performance, but it also has problems such as interfacial stress concentration, premature detachment of hollow spheres, reduced grinding wheel life, pore collapse and pore size shrinkage, and weak interfacial bonding.

[0004] Although invention patent application CN 109202750 A discloses a hollow packed abrasive grain and its preparation method, as well as a superhard abrasive, the hollow packed abrasive grain forms abrasive microspheres with a hollow structure, which improves the bonding strength of the packed abrasive grain and reduces the complexity of the manufacturing of the packed abrasive grain; however, its preparation process requires the addition of a large amount of pore-forming agent, which increases the raw material cost and causes the grinding wheel to crack. In addition, the patent application uses a rolling spherical granulation method, which makes it difficult to achieve a particle size of 10 μm for the hollow packed abrasive grain. Summary of the Invention

[0005] In view of this, the main objective of the present invention is to provide a hollow agglomerated diamond microsphere with a sphericity of over 90%, a hollow structure and thin film characteristics, and a thin wall containing both diamond and ceramic binder. This microsphere can serve as a pore-forming agent and abrasive, solving the problem of uneven pore distribution and improving the sharpness and self-sharpening properties of abrasive tools.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: A hollow agglomerated diamond microsphere is mainly prepared by using a first ceramic binder and diamond micro powder as raw materials, alkoxide as binder and water as solvent to prepare a uniformly mixed ceramic slurry; granulating the ceramic slurry by centrifugal spray granulation to prepare a hollow agglomerated diamond microsphere green body; and calcining the hollow agglomerated diamond microsphere green body at high temperature.

[0007] The alkoxide, as the main material for forming the hollow structure in the preparation of hollow aggregated diamond microspheres, can be one or more of silanolates, titanium alkoxides, aluminum alkoxides, zirconium alkoxides, etc., specifically such as tetraethyl orthosilicate, tetraethyl titanate, triisopropylaluminum, tetraisopropylzirconium, etc.

[0008] To balance wear resistance and self-sharpening properties, the ceramic slurry, by mass percentage, consists of 3%–22% diamond micron powder, 3%–18% of a 0.01–5 μm first ceramic binder, 0%–5% of a first pore-forming agent, 5%–15% of alkoxide and water, with water as the balance.

[0009] To prepare hollow agglomerated diamond microspheres with high sphericity and no collapse, the granulation process includes: placing the ceramic slurry in the centrifugal spray granulator for granulation to obtain hollow agglomerated diamond microsphere preforms with a particle size of 10–150 μm; wherein the frequency of the atomizer is 30–50 Hz and the internal temperature of the atomization chamber is 180–230 ℃.

[0010] To improve the strength of hollow agglomerated diamond microspheres and facilitate their classification and movement, the high-temperature calcination treatment step includes: holding the hollow agglomerated diamond microsphere blank in a muffle furnace at 300-350℃ for 1-2 h and then at 580-630℃ for 1-3 h, followed by sieving to remove the first pore-forming agent and pre-sintering, and then classifying the particles by sieve.

[0011] A second objective of this invention is to provide an application of the aforementioned hollow agglomerated diamond microspheres as a pore-forming agent in the preparation of diamond abrasives; this can solve the problem of uneven pore distribution. The diamond abrasive can be a diamond grinding wheel, a diamond grinding disc, a diamond cutting disc, etc.

[0012] Furthermore, the application includes: using the above-mentioned hollow aggregated diamond microspheres as abrasives to prepare diamond abrasives by gel casting method; this can also avoid environmental pollution during the removal of organic pore-forming agents, and at the same time help to prepare abrasives with high sharpness and high self-sharpening properties.

[0013] A third objective of this invention is to provide a method for preparing diamond abrasives to improve their self-sharpening properties, sharpness, and service life. To achieve this objective, the specific technical solution is as follows: A method for preparing a diamond abrasive includes: using the above-mentioned hollow aggregated diamond microspheres and diamond with a D50 particle size of 0.01 to 10 μm as abrasives, and employing a gel casting method to prepare the diamond abrasive.

[0014] To ensure the diamond abrasive tool possesses high sharpness and self-sharpening properties, and to avoid problems such as stress concentration, weak interfacial bonding, and uneven pore distribution caused by thermal expansion coefficient mismatch during operation, the raw materials for preparing the diamond abrasive tool, by mass percentage, include: 10%–70% hollow aggregated diamond microspheres, 3%–49% diamond with a D50 particle size of 0.01–10 μm, 3%–42% second ceramic binder with a D50 particle size of 0.01–5 μm, 0%–7% second organic pore-forming agent with a D50 particle size of 0.01–10 μm, 3%–8% amide mixed solution, 2%–5% initiator solution, and 1%–3% catalyst solution. The amide mixed solution has a concentration of 3–10 wt% and is prepared by uniformly mixing acrylamide and N,N-methylenebisacrylamide at a mass ratio of 25–29:0.5–1. The initiator solution has a concentration of 10–15 wt%, and the catalyst solution has a concentration of 0.5–2 wt%. wt%.

[0015] A fourth objective of this invention is to provide a diamond abrasive tool prepared by the above-described method.

[0016] A fifth objective of this invention is to provide an application of the aforementioned diamond abrasive tool in semiconductor material processing. The semiconductor material includes sapphire, silicon wafers, silicon carbide wafers, etc. Preferably, the application of the aforementioned diamond abrasive tool in semiconductor material grinding processing includes, for example, using the aforementioned diamond micron abrasive tool as a silicon carbide thinning wheel for thinning silicon carbide wafers.

[0017] Therefore, compared with the prior art, the technical solution provided by the present invention, using alkoxides as a binder, can avoid the depressions in the hollow agglomerated diamond microspheres caused by the low bonding strength of organic materials, and can achieve the preparation of high-sphericity agglomerated hollow diamond spheres. Furthermore, using hollow agglomerated diamond microspheres as a pore-forming agent can avoid problems such as stress concentration, weak interfacial bonding, and uneven pore distribution caused by thermal expansion coefficient mismatch. Using hollow agglomerated diamond microspheres as raw materials can avoid environmental pollution during the removal of organic pore-forming agents and also helps in the preparation of grinding wheels with high sharpness and high self-sharpening properties. Therefore, the present invention, using the above-mentioned hollow agglomerated diamond microspheres as a pore-forming agent and abrasive grains, can solve the problem of uneven pore distribution in diamond grinding wheels and improve the sharpness and self-sharpening properties of the grinding wheel. Attached Figure Description

[0018] Figure 1 This is a SEM image of the hollow aggregated diamond microspheres prepared in Example 1 of the present invention; Figure 2 This is a photograph of the diamond grinding wheel obtained in Example 1 of the present invention; Figure 3 This is a SEM image of the hollow aggregated diamond microspheres used in Comparative Example 1 of this invention; Figure 4 This is a SEM image of the hollow aggregated diamond microspheres prepared in Comparative Example 2 of the present invention; Figure 5 This is a SEM image of the hollow aggregated diamond microspheres used in Comparative Example 3 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0020] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0021] In this invention, unless otherwise specified and / or stated, all numerical values ​​involving component amounts are "by weight". Unless otherwise specified, the terminology used in this invention are common terms in the relevant field. Unless otherwise specified, the preparation processes, testing methods, etc., used in the various embodiments are conventional methods well known to those skilled in the art, and the raw materials and equipment used can be obtained from publicly available commercial sources.

[0022] This invention mainly provides a hollow agglomerated diamond microsphere with a sphericity of over 90%, which has a hollow structure and thin film characteristics, and the thin wall contains both diamond and ceramic binder. Using this hollow agglomerated diamond microsphere as a pore-forming agent and abrasive can solve the problem of uneven pore distribution in diamond grinding wheels and improve the sharpness and self-sharpening properties of the grinding wheel.

[0023] To achieve the above objectives, the present invention adopts the following specific implementation technical solutions: A hollow agglomerated diamond microsphere is mainly prepared by using a first ceramic binder and diamond micro powder as raw materials, alkoxide as binder, and water as solvent to prepare a uniformly mixed ceramic slurry; granulating the ceramic slurry by centrifugal spray granulation to prepare a hollow agglomerated diamond microsphere green body; and calcining the hollow agglomerated diamond microsphere green body at 550-650℃.

[0024] The alkoxide is one or a mixture of silanolates, titanium alkoxides, aluminum alkoxides, zirconium alkoxides, etc., specifically such as tetraethyl orthosilicate, tetraethyl titanate, triisopropylaluminum, tetraisopropylzirconium, etc. In this invention, using alkoxides as a binder allows for the preparation of hollow agglomerated diamond microspheres from ceramic slurries with a solid content of less than 40%, avoiding the depressions in the hollow agglomerated diamond microsphere blanks caused by low bonding strength of organic matter, and achieving the preparation of high-sphericity hollow agglomerated diamond microspheres with a sphericity of at least 90%. The solid content of the ceramic slurry can be 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 3%, etc. Low solid content ceramic slurries are beneficial for the preparation of hollow spheres.

[0025] The first ceramic binder is an existing material, and its composition, by mass percentage, includes: 40-60% SiO2, 15-30% B2O3, 5-15% Al2O3, 5-10% alkali metal oxides, and 5-10% alkaline earth metal oxides; wherein the alkali metal oxides are one or more of Na2O, K2O, and Li2O, and the alkaline earth metal oxides are one or more of CaO, MgO, and BaO.

[0026] To balance wear resistance and self-sharpening properties, the ceramic slurry, by mass percentage, mainly consists of 3%–22% diamond micron powder, 3%–18% of a 0.01–5 μm first ceramic binder, 0%–5% of a first pore-forming agent, 4%–15% of an alkoxide, and water, with water as the balance. The solid content of the ceramic slurry is preferably 10%–40%. The preparation process may include: ultrasonically stirring the diamond micron powder, the first ceramic binder, the pore-forming agent, the alkoxide, and deionized water until a uniform mixture is obtained. Preferably, the D50 particle size of the diamond microparticles is 0.01–10 μm, such as 0.01 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.; the D50 particle size of the ceramic binder is 0.01–10 μm, such as 0.01 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc.; the D50 particle size of the pore-forming agent is 0.01–10 μm, such as 0.01 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. The first pore-forming agent can be one or more organic pore-forming agents such as PMMA microspheres and PS microspheres.

[0027] To prepare hollow agglomerated diamond microspheres with high sphericity and non-collapse, the granulation process includes: placing the ceramic slurry in the centrifugal spray granulator for granulation to obtain hollow agglomerated diamond microsphere preforms with a particle size of 10–150 μm; wherein the atomizer frequency is 30–50 Hz, and the internal temperature of the atomization chamber is 180–230 ℃. The internal temperature of the atomization chamber should not be too low, as this will result in incomplete drying; if it is too high, it will waste energy.

[0028] To improve the strength of hollow agglomerated diamond microspheres and facilitate their classification and movement, the high-temperature calcination treatment step includes: holding the hollow agglomerated diamond microsphere blank in a muffle furnace at 300–350 °C for 1–2 h, then at 580–630 °C for 1–3 h, followed by sieving to remove the first pore-forming agent and pre-sintering, and then classifying the particles by particle size using a sieve. The purpose of the two-step heating in this high-temperature calcination treatment is: the first step, low-temperature heating, is to remove the pore-forming agent, and the second step, high-temperature heating, is to improve the strength of the hollow agglomerated diamond microspheres.

[0029] A second objective of this invention is to provide an application of the aforementioned hollow agglomerated diamond microspheres as a pore-forming agent in the preparation of diamond abrasives; this can solve the problem of uneven pore distribution. The diamond abrasive can be a diamond grinding wheel, a diamond grinding disc, a diamond cutting disc, etc.

[0030] Furthermore, the application includes: using the above-mentioned hollow aggregated diamond microspheres as abrasives to prepare diamond abrasives by gel casting method; this can also avoid environmental pollution during the removal of organic pore-forming agents, and at the same time help to prepare abrasives with high sharpness and high self-sharpening properties.

[0031] A third objective of this invention is to provide a method for preparing diamond abrasives to improve their self-sharpening properties, sharpness, and service life. To achieve this objective, the specific technical solution is as follows: A method for preparing a diamond abrasive includes: using the above-mentioned hollow aggregated diamond microspheres and diamond with a D50 particle size of 0.01 to 10 μm as abrasives, and employing a gel casting method to prepare the diamond abrasive.

[0032] To ensure the diamond abrasive tool possesses high sharpness and self-sharpening properties, and to avoid problems such as stress concentration, weak interfacial bonding, and uneven pore distribution caused by thermal expansion coefficient mismatch during operation, the raw materials for preparing the diamond abrasive tool, by mass percentage, include: 10%–70% hollow aggregated diamond microspheres, 3%–49% diamond with a D50 particle size of 0.01–10 μm, 3%–42% second ceramic binder with a D50 particle size of 0.01–5 μm, 0%–7% second organic pore-forming agent with a D50 particle size of 0.01–10 μm, 3%–8% amide mixed solution, 2%–5% initiator solution, and 1%–3% catalyst solution. The amide mixed solution has a concentration of 3–10 wt% and is prepared by uniformly mixing acrylamide and N,N-methylenebisacrylamide at a mass ratio of 25–29:0.5–1. The initiator solution has a concentration of 10–15 wt%, and the catalyst solution has a concentration of 0.5–2 wt%. wt%.

[0033] The second ceramic binder is an existing material, and its composition, by mass percentage, includes: 40-60% SiO2, 15-30% B2O3, 5-15% Al2O3, 5-10% alkali metal oxides, and 5-10% alkaline earth metal oxides; wherein the alkali metal oxides are one or more of Na2O, K2O, and Li2O, and the alkaline earth metal oxides are one or more of CaO, MgO, and BaO. Preferably, the second ceramic binder has the same composition as the first ceramic binder. The second organic pore-forming agent can be one or more of PMMA microspheres, PS microspheres, etc. Preferably, the second organic pore-forming agent is the same as the first pore-forming agent.

[0034] As one embodiment, the preparation method includes: Preparation of slurry: First, uniformly mix 3%–8% of the amide mixed solution, 2%–5% of the initiator solution, 1%–3% of the catalyst solution, 10%–70% of the above hollow aggregated diamond microspheres, 3%–49% of diamond with a D50 particle size of 0.01–10 μm, 3%–42% of ceramic binder with a D50 particle size of 0.01–5 μm, and 0%–7% of the second organic pore-forming agent with a D50 particle size of 30–500 μm to prepare a hollow microsphere mixed slurry; Preparation of the blank: The hollow microsphere mixture slurry is poured into a mold, dried, and demolded to obtain a diamond grinding tool blank; Preparation of abrasives: The diamond abrasive blank is sintered to prepare diamond abrasives.

[0035] The mold is made of materials such as acrylic sheet, glass sheet, and ceramic.

[0036] The steps for preparing the abrasive include: first, placing the diamond abrasive blank in a muffle furnace and sintering it at 600℃~700℃ for 2~3 h; then, processing it according to the predetermined structure of the diamond abrasive and bonding it to the abrasive substrate; and finally, after modification, the diamond abrasive product can be obtained.

[0037] A fourth objective of this invention is to provide a diamond abrasive tool prepared by the above-described method.

[0038] A fifth objective of this invention is to provide an application of the aforementioned diamond abrasive tool in semiconductor material processing. The semiconductor material includes sapphire, silicon wafers, silicon carbide wafers, etc. Preferably, the application of the aforementioned diamond abrasive tool in semiconductor material grinding processing includes, for example, using the aforementioned diamond micron abrasive tool as a silicon carbide thinning wheel for thinning silicon carbide wafers.

[0039] The technical solutions protected by this invention will be further explained and illustrated below through specific embodiments.

[0040] The ceramic binders used in the following embodiments and comparative examples are composed of 50% SiO2, 20% B2O3, 10% Al2O3, 4% Na2O, 3% K2O, 3% Li2O, 4% CaO, 4% MgO, and 2% BaO by mass percentage.

[0041] Example 1: Hollow spheres containing PMMA microspheres + gel molding containing PMMA microspheres This embodiment provides a hollow agglomerated diamond microsphere and its preparation method. The preparation method of the hollow agglomerated diamond microsphere specifically includes the following steps: (Q1) Weigh 5% of diamond with a D50 particle size of 1.5 μm, 5% of ceramic binder with a D50 particle size of 1.5 μm, 5% of PMMA microspheres with a D50 particle size of 10 μm, 5% of tetraethyl orthosilicate, and 80% of deionized water and place them in a container. Then, prepare a uniformly mixed ceramic slurry by ultrasonic mechanical stirring. (Q2) The granulation process was carried out by a centrifugal spray granulator and sieved to obtain hollow agglomerated diamond microsphere preforms with a D50 particle size of 50-80 μm; the frequency of the atomizer was 35 Hz and the internal temperature of the cavity was 200 ℃. (Q3) The atomized granulated D50 hollow agglomerated diamond microsphere preforms with a particle size of 50-80 μm were held in a muffle furnace at 320 ℃ and 600 ℃ for 2 h respectively to remove the PMMA microsphere pore-forming agent and perform pre-sintering. The preforms were then subjected to particle size classification using a sieve to obtain the desired product. Figure 1 The D50 hollow aggregated diamond microspheres shown have a particle size of 50–80 μm.

[0042] This embodiment also provides an application of the above-mentioned hollow agglomerated diamond microspheres in the preparation of diamond grinding wheels. Specifically, the method for preparing the diamond grinding wheel includes the following steps: (S1) Weigh the raw materials for preparing diamond grinding wheels according to the following mass percentages, and mix the raw materials evenly to obtain a hollow microsphere slurry; wherein, the raw materials for preparing diamond grinding wheels include 8% of a 10% amide mixed solution prepared by weighing acrylamide and N,N-methylenebisacrylamide in a mass ratio of 29:1, 2% of a 10% ammonium persulfate solution, 3% of a 0.5% tetramethylethylenediamine solution, 70% of the hollow agglomerated diamond microspheres with a D50 particle size of 50-80 μm provided in this embodiment, 8% of diamond with a D50 particle size of 1.5 μm, 4% of ceramic binder with a D50 particle size of 0.5-1.5 μm, and 5% of PMMA microsphere pore-forming agent with a D50 particle size of 60 μm. Mix the weighed materials evenly to obtain a hollow microsphere slurry; (S2) The hollow microsphere mixture slurry is introduced into an acrylic mold and dried in an oven at 45 ℃ for more than 48 h to make it completely dry and demolded to obtain a diamond abrasive blank. (S3) The diamond grinding wheel blank is placed in a muffle furnace and sintered at 650 °C for 2.5 h. Then, it is cut according to the grinding wheel drawing and bonded to the grinding wheel base. After modification, a diamond grinding wheel is obtained, as shown below. Figure 2 As shown.

[0043] Example 2: Hollow spheres containing PMMA microspheres + gel casting containing PMMA microspheres + different alkoxides This embodiment provides a hollow agglomerated diamond microsphere and its preparation method. The preparation method of the hollow agglomerated diamond microsphere specifically includes the following steps: (Q1) Weigh 5% of diamond with a D50 particle size of 0.5 μm, 5% of ceramic binder with a D50 particle size of 0.5 μm, 5% of PMMA microsphere pore-forming agent with a D50 particle size of 5 μm, 5% of tetraethyl titanate, and 80% of deionized water and place them in a container. Stir the mixture with ultrasonic mechanical stirring to prepare a uniformly mixed ceramic slurry. (Q2) The granulation process was carried out by a centrifugal spray granulator and sieved to obtain hollow agglomerated diamond microsphere preforms with a D50 particle size of 10-30 μm; the frequency of the atomizer was 40 Hz and the internal temperature of the cavity was 210 ℃. (Q3) The hollow agglomerated diamond microsphere preform with a particle size of 10-30 μm after atomization and granulation was kept in a muffle furnace at 330 ℃ and 590 ℃ for 2 h respectively to remove the PMMA microsphere pore-forming agent and perform pre-sintering. The preform was then classified by particle size through a sieve to obtain hollow agglomerated diamond microspheres with a particle size of 10-30 μm.

[0044] This embodiment also provides an application of the above-mentioned hollow agglomerated diamond microspheres in the preparation of diamond grinding wheels. Specifically, the method for preparing the diamond grinding wheel includes the following steps: (S1) Weigh the raw materials for preparing diamond grinding wheels according to the following mass percentages, and mix the raw materials evenly to obtain a hollow microsphere slurry; wherein, the raw materials for preparing diamond grinding wheels include 8% of acrylamide and N,N-methylenebisacrylamide mixed solution with a mass ratio of 29:1, 2% of ammonium persulfate solution, 3% of tetramethylethylenediamine solution, 70% of the hollow agglomerated diamond microspheres with a D50 particle size of 10-30 μm obtained in this embodiment, 8% of diamond with a D50 particle size of 0.5 μm, 4% of ceramic binder with a D50 particle size of 0.5 μm, and 5% of PMMA microspheres with a D50 particle size of 60 μm; (S2) The hollow microsphere mixture slurry is introduced into an acrylic mold and dried in an oven at 45 ℃ for more than 48 h to make it completely dry and demolded to obtain a diamond abrasive blank. (S3) The diamond grinding wheel blank is placed in a muffle furnace and sintered at 610 °C for 3 h. Then it is cut according to the grinding wheel drawing and bonded to the grinding wheel base. After modification, a diamond grinding wheel is obtained.

[0045] Example 3: Hollow spheres containing PMMA microspheres + gel casting containing PMMA microspheres + different alkoxides This embodiment provides a hollow agglomerated diamond microsphere and its preparation method. The preparation method of the hollow agglomerated diamond microsphere specifically includes the following steps: (Q1) Weigh 22% of diamond with a D50 particle size of 9 μm, 18% of ceramic binder with a D50 particle size of 1.5 μm, 3% of PMMA microspheres with a D50 particle size of 10 μm, 15% of triisopropylaluminum, and 62% of deionized water and place them in a container. Then, prepare a uniformly mixed ceramic slurry by ultrasonic mechanical stirring. (Q2) The granulation process was carried out by a centrifugal spray granulator and sieved to obtain hollow agglomerated diamond microsphere preforms with a D50 particle size of 50-70 μm; the frequency of the atomizer was 45 Hz and the internal temperature of the cavity was 200 ℃. (Q3) The hollow agglomerated diamond microspheres with a particle size of 50-80 μm after atomization and granulation were pre-sintered in a muffle furnace at 620℃ for 2 h and then classified by particle size through a sieve to obtain hollow agglomerated diamond microspheres with a particle size of 50-70 μm.

[0046] This embodiment also provides an application of the above-mentioned hollow agglomerated diamond microspheres in the preparation of diamond grinding wheels. Specifically, the method for preparing the diamond grinding wheel includes the following steps: (S1) Weigh the raw materials for preparing diamond grinding wheels according to the following mass percentages, and mix the raw materials evenly to obtain a hollow microsphere slurry; wherein, the raw materials for preparing diamond grinding wheels include 8% of acrylamide and N,N-methylenebisacrylamide mixed solution with a mass ratio of 29:1, 3% of ammonium persulfate solution, 2% of tetramethylethylenediamine solution, 10% of the hollow agglomerated diamond microspheres with a D50 particle size of 50-70 μm prepared in this embodiment, 48% of diamond with a D50 particle size of 9 μm, 24% of ceramic binder with a D50 particle size of 0.5 μm, and 5% of PMMA microspheres with a D50 particle size of 70 μm; (S2) The hollow microsphere mixture slurry is introduced into an acrylic mold and dried in an oven at 45 ℃ for more than 48 h to make it completely dry and demolded to obtain a diamond abrasive blank. (S3) The diamond grinding wheel blank is placed in a muffle furnace and sintered at 650 °C for 3 h. Then it is cut according to the grinding wheel drawing and bonded to the grinding wheel base. After modification, a diamond grinding wheel is obtained.

[0047] Example 4: Hollow spheres containing PS microspheres + gel molding containing PS microspheres This embodiment provides a hollow agglomerated diamond microsphere and its preparation method. The preparation method of the hollow agglomerated diamond microsphere specifically includes the following steps: (Q1) Weigh 12% of diamond with a D50 particle size of 1.5 μm, 10% of ceramic binder with a D50 particle size of 1.5 μm, 3% of PS microspheres with a D50 particle size of 10 μm, 7% of tetraethyl orthosilicate, and 68% of deionized water and place them in a container. Then, prepare a uniformly mixed ceramic slurry by ultrasonic mechanical stirring. (Q2) The granulation process was carried out by a centrifugal spray granulator and sieved to obtain hollow agglomerated diamond microsphere preforms with a D50 particle size of 30-70 μm; the frequency of the atomizer was 35 Hz and the internal temperature of the cavity was 200 ℃. (Q3) The hollow agglomerated diamond microsphere preform with a particle size of 30-70 μm after atomization and granulation was kept in a muffle furnace at 320 °C and 600 °C for 2 h respectively. The pore-forming agent was removed and pre-sintered. The particle size was then classified by sieve to obtain hollow agglomerated diamond microspheres with a particle size of 30-70 μm.

[0048] This embodiment also provides an application of the above-mentioned hollow agglomerated diamond microspheres in the preparation of diamond grinding wheels. Specifically, the method for preparing the diamond grinding wheel includes the following steps: (S1) Weigh the raw materials for preparing diamond grinding wheels according to the following mass percentages, and mix the raw materials evenly to obtain a hollow microsphere slurry; wherein, the raw materials for preparing diamond grinding wheels include 8% of acrylamide and N,N-methylenebisacrylamide mixed solution with a mass ratio of 29:1, 2% of ammonium persulfate solution, 3% of tetramethylethylenediamine solution, 50% of the hollow agglomerated diamond microspheres with a D50 particle size of 30-70 μm obtained in this embodiment, 18% of diamond with a D50 particle size of 1.5 μm, 14% of ceramic binder with a D50 particle size of 1 μm, and 5% of PMMA microspheres with a D50 particle size of 60 μm; (S2) The hollow microsphere mixture slurry is introduced into an acrylic mold and dried in an oven at 45 ℃ for more than 48 h to make it completely dry and demolded to obtain a diamond abrasive blank. (S3) The diamond grinding wheel blank is placed in a muffle furnace and sintered at 650 °C for 2 h. Then it is cut according to the grinding wheel drawing and bonded to the grinding wheel base. After modification, a diamond grinding wheel is obtained.

[0049] Example 5: Hollow spheres without PMMA microspheres + gel molding containing PMMA microspheres This embodiment provides a hollow agglomerated diamond microsphere and its preparation method, which is basically the same as the hollow agglomerated diamond microsphere and its preparation method provided in Example 1. The main difference is that PMMA microspheres are not added in step (Q1), the content of deionized water is increased to 85%, and other steps and parameters are the same.

[0050] This embodiment also provides an application of the above-mentioned hollow aggregated diamond microspheres in the preparation of diamond grinding wheels, which is basically the same as the preparation method of the diamond grinding wheel provided in Example 1, the main difference being: this embodiment uses... Figure 3 The hollow aggregated diamond microspheres shown are used instead of those in Example 1, with the other steps and parameters being the same.

[0051] Example 6: Hollow spheres without PMMA microspheres + gel molding without PMMA microspheres This embodiment provides a diamond grinding wheel and its preparation method, which is basically the same as the diamond grinding wheel and its preparation method provided in Example 5. The main difference is that PMMA microspheres are not added in step (S1), and the amount of ceramic binder is increased to 9%. Other steps and parameters are the same.

[0052] Example 7: Hollow spheres containing PMMA microspheres + gel molding without PMMA microspheres This embodiment provides a diamond grinding wheel and its preparation method, which is basically the same as the diamond grinding wheel and its preparation method provided in Example 1. The main difference is that PMMA microspheres are not added in step (S1), and the amount of ceramic binder is increased to 9%. Other steps and parameters are the same.

[0053] Comparative Examples 1-3 Each comparative example provides a diamond grinding wheel and its preparation method, which are basically the same as the diamond grinding wheel and its preparation method provided in Example 1, with the main differences as follows: The main difference between the hollow agglomerated diamond microspheres used in Comparative Example 1 and those in the examples is that a polyvinyl alcohol solution of the same concentration is used instead of silanol salts; other steps and parameters are the same. The hollow agglomerated diamond microspheres prepared in this comparative example are as follows: Figure 3 As shown; The main difference between Comparative Example 2 and the previous example is that the hollow agglomerated diamond microspheres used are: a carboxymethyl cellulose solution of the same concentration is used instead of silanol salts; other steps and parameters are the same. The hollow agglomerated diamond microspheres prepared in this comparative example are as follows: Figure 4 As shown; The main difference between the hollow agglomerated diamond microspheres used in Comparative Example 3 and those in the examples is that a starch solution of the same concentration is used instead of silanol salts; other steps and parameters are the same. The hollow agglomerated diamond microspheres prepared in this comparative example are as follows: Figure 5 As shown.

[0054] The following tests were conducted on the diamond grinding wheels provided in Examples 1-7 and Comparative Examples 1-3, and the results are shown in Table 1.

[0055] (1) Porosity determination method: Weigh the cut sample strip and take its weight m1. Place the sample in a vacuum chamber and add distilled water until it completely covers the sample. Turn on the vacuum extractor until the remaining pressure is less than 0.0013 MPa. Evacuate the air until no bubbles appear in the sample and take out the sample. Place the saturated sample on the instrument and quickly weigh the saturated sample in air m2 (when using the boiling method, use multiple layers of water-saturated gauze to wipe away the water adhering to the sample surface), accurate to 0.0001 g. Place the saturated sample in water and weigh its weight in water m3, accurate to 0.0001 g. Wherein, porosity (%) = (m3-m1 / (m3-m2)×100.

[0056] (2) Processing efficiency: Each diamond grinding wheel was used to grind the 3-inch wafer on the OKAMOTO grinding machine. The grinding wheel speed was 1500 rpm, and the grinding wheel was used to process at a feed rate of 0.2 μm / s while ensuring a current value of about 14 A.

[0057] (3) Bending strength: Tested according to the current industry standard GB / T 6409-2009 "Superhard Abrasive Products".

[0058] (4) Surface roughness: The surface roughness of the wafer after grinding was tested using a SuperViewW1 series white light interferometer.

[0059] Table 1 Performance test results of various diamond grinding wheels object Porosity (%) Processing efficiency (μm / s) Flexural strength (MPa) SiC wafer surface roughness (nm) Example 1 60 0.3 40 13.1 Example 2 70 0.1 33 3.1 Example 3 55 0.4 40 20.2 Example 4 60 0.3 40 13.6 Example 5 25 0.2 50 13.2 Example 6 20 0.1 55 17.3 Example 7 30 0.2 45 15.1 Comparative Example 1 30 0.2 45 26.3 Comparative Example 2 30 0.2 40 26.2 Comparative Example 3 30 0.2 40 26.6 As can be seen from Table 1: Compared with Example 1, the hollow agglomerated diamond microspheres provided in Example 5 do not have additional PMMA microspheres added as pore-forming agent, which reduces the porosity of the diamond grinding wheel and reduces the grinding efficiency. This is mainly because the pore-forming agent used in the hollow agglomerated diamond microspheres is used to improve the self-sharpening ability of the diamond in the microspheres.

[0060] Compared to Example 1, Example 6 did not add additional PMMA microspheres as a pore-forming agent during the entire preparation process of the diamond grinding wheel. The role of the pore-forming agent in hollow aggregated diamond microspheres is to improve the self-sharpening ability of the diamond within the microspheres; the role of the pore-forming agent in the gel casting method for preparing diamond grinding wheels is to improve the microsphere shedding ability. Therefore, the diamond grinding wheel prepared in Example 6 has slow processing efficiency, poor self-sharpening properties, and high surface roughness of the workpiece.

[0061] Compared with Example 1, Example 7 did not add a second pore-forming agent, PMMA microspheres, during the preparation of diamond grinding wheels by gel casting. This resulted in a stronger holding capacity of the diamond microspheres in the diamond grinding wheels. This is mainly because, during the preparation of diamond grinding wheels by gel casting, the role of the pore-forming agent is to improve the bonding strength between the microspheres.

[0062] Combination Figure 1 and 3 5. Compared with Example 1, in Comparative Examples 1-3, polyvinyl alcohol, carboxymethyl cellulose, and starch were used instead of alkoxides as binders, respectively. Since these three substances, as organic binders, have low bonding strength with other raw materials, while alkoxides have high strength after hydrolysis. Therefore, the use of alkoxides in Example 3 can avoid the depressions in the hollow agglomerated diamond microsphere preform caused by the low bonding strength of organic materials, thereby achieving the preparation of high-sphericity hollow agglomerated diamond microspheres with a sphericity of at least 90%.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A hollow aggregated diamond microsphere, characterized in that, The material is mainly prepared by the following method: using a first ceramic binder and diamond micro powder as raw materials, alkoxide as binder and water as solvent, a uniformly mixed ceramic slurry is prepared; the ceramic slurry is granulated by centrifugal spray granulation to prepare hollow agglomerated diamond microsphere green bodies; the hollow agglomerated diamond microsphere green bodies are subjected to high-temperature calcination.

2. The hollow aggregated diamond microspheres according to claim 1, characterized in that, The alkoxide is one or a mixture of silicon alkoxides, titanium alkoxides, aluminum alkoxides and zirconium alkoxides.

3. The hollow aggregated diamond microspheres according to claim 1 or 2, characterized in that, The ceramic slurry, by weight percentage, consists of 3%–22% diamond micron powder, 3%–18% of the first ceramic binder of 0.01–5 μm, 0%–5% of the first pore-forming agent, 5%–15% of the alkoxide and water, with water as the balance.

4. The hollow aggregated diamond microspheres according to claim 3, characterized in that, The granulation process includes: placing the ceramic slurry in the centrifugal spray granulator for granulation to obtain the hollow agglomerated diamond microsphere preform with a particle size of 10-150 μm; wherein the frequency of the atomizer is 30-50 Hz and the internal temperature of the atomizing chamber is 180-230℃.

5. The hollow aggregated diamond microspheres according to claim 1 or 2, characterized in that, The high-temperature calcination process includes: holding the hollow agglomerated diamond microsphere preform at 300-350°C for 1-2 hours in a muffle furnace, then holding it at 580-630°C for 1-3 hours, then sieving it to remove the first pore-forming agent and perform pre-sintering, and then classifying the particles by sieve.

6. The use of hollow agglomerated diamond microspheres as described in any one of claims 1 to 5 as a pore-forming agent in the preparation of diamond abrasives.

7. A method for preparing a diamond abrasive, comprising: Using hollow aggregated diamond microspheres as described in any one of claims 1 to 5 and diamond with a D50 particle size of 0.01 to 10 μm as abrasives, a diamond abrasive tool is made by gel casting.

8. The preparation method according to claim 7, characterized in that, The raw materials for preparing the diamond abrasive, by mass percentage, include: 10%–70% hollow aggregated diamond microspheres, 3%–49% diamond with a D50 particle size of 0.01–10 μm, 3%–42% second ceramic binder with a D50 particle size of 0.01–5 μm, 0%–7% second organic pore-forming agent with a D50 particle size of 0.01–10 μm, 3%–8% amide mixed solution, 2%–5% initiator solution, and 1%–3% catalyst solution. The amide mixed solution has a concentration of 3–10 wt% and is prepared by uniformly mixing acrylamide and N,N-methylenebisacrylamide in a mass ratio of 25–29:0.5–1. The initiator solution has a concentration of 10–15 wt%, and the catalyst solution has a concentration of 0.5–2 wt%.

9. A diamond abrasive tool prepared by the method according to claim 7 or 8, wherein, The diamond abrasive tools include diamond grinding wheels, diamond grinding discs, or diamond cutting discs.

10. The application of the diamond abrasive tool according to claim 9 in semiconductor material processing.

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