Agglomerated diamond as well as preparation method and application thereof

Abstract

The invention provides agglomerated diamond as well as a preparation method and application thereof, and the preparation method comprises the following steps: taking a SiC precursor and diamond as raw materials, and preparing SiC precursor diamond composite powder by adopting a dissolving and dipping method; carrying out modification treatment on the SiC precursor diamond composite powder; carrying out ball milling on the modified composite powder, and granulating; and carrying out sand burying and vacuum sintering on the granulated particles, and sorting to obtain the agglomerated diamond. The agglomerated diamond prepared by the preparation method has high hardness and high wear resistance, a processed wafer has excellent surface quality, and the agglomerated diamond has higher processing efficiency and longer service life under the condition of the same wafer surface roughness.

Description

Technical Field

[0001] The invention relates to the field of diamonds, and in particular to agglomerated diamonds and a preparation method and application thereof. Background Art

[0002] Since the third-generation semiconductor materials represented by SiC have a wider bandgap, higher thermal conductivity and higher radiation resistance, this type of material is more suitable for making high-temperature, high-frequency, radiation-resistant and high-power devices, and the processing accuracy of the SiC substrate will directly affect the device performance. At present, the processing technology of SiC wafers can be simply divided into cutting, rough grinding, fine grinding and polishing. The purpose of grinding is to remove scratches and damage layers on the SiC surface caused by the cutting process. Due to the high hardness of SiC, high-hardness abrasives must be used in the grinding process. In order to obtain high grinding efficiency, the current SiC single crystal substrate grinding liquid usually selects polycrystalline diamond or agglomerated diamond grinding liquid. Among them, agglomerated diamond is a fine-grained abrasive bonded by a binder, and the shape is mostly spherical and quasi-spherical with evenly distributed cutting edges.

[0003] For example, the invention patent with application publication number CN117003581A discloses a kind of agglomerated diamond and its preparation method and application. This method ensures the sphericity of agglomerated diamond through a special suspension dispersion granulation method and suspension dispersion sintering method, avoiding the poor sphericity caused by ordinary crushing granulation, and the ordinary static and aggregated sintering in a container, which leads to the agglomerated diamond being difficult to disperse during sintering, and the sintering temperature is too high, which makes the agglomerated diamond agglomerate and the sphericity poor. The agglomerated diamond prepared by this method has excellent sphericity, which is conducive to grinding and polishing. However, this method still directly uses ceramic binder as the binder raw material, and uses sol-gel method for mixing. Due to the difference in hardness and wear resistance between ceramic binder and SiC, the service life of ceramic binder diamond and the grinding efficiency of workpieces under the same surface roughness conditions need to be improved. Summary of the invention

[0004] In order to make the prepared agglomerated diamond have high hardness and high wear resistance, the wafer processed by using the agglomerated diamond as an abrasive has excellent surface quality, and under the condition of the surface roughness of the same wafer, it has higher processing efficiency and abrasive service life, the technical scheme adopted by the present invention is: a preparation method of agglomerated diamond, comprising the following steps:

[0005] Preparation of composite powder: SiC precursor and diamond are used as raw materials, and SiC precursor diamond composite powder is prepared by dissolution impregnation method;

[0006] Modification: Modification treatment is performed on SiC precursor diamond composite powder;

[0007] Ball milling granulation: the modified composite powder is ball milled and then granulated;

[0008] The granulated particles are subjected to sand-embedded vacuum sintering and then sorted to obtain agglomerated diamonds.

[0009] Based on the above, the steps of preparing the composite powder include:

[0010] Polycarbosilane is dissolved in toluene, xylene, n-hexane, acetone and ethanol solvents, diamond with a median particle size of 0.25 μm to 3.5 μm is added to the solvent, and the mixture is placed in an oil bath for stirring and heat preservation, and then placed in an oven for drying to obtain SiC precursor diamond composite powder, wherein the mass percentage of diamond is 70% to 90% and the mass percentage of polycarbosilane is 10% to 30%.

[0011] Specifically, the median particle size of diamond can be selected as 0.25 μm, 0.5 μm, 1 μm, 1.5 μm, 2.5 μm, 3 μm and 3.5 μm. The temperature of the oil bath pot is 90° C. to 130° C., and the insulation time is 8 h to 12 h. The temperature of the oven is 150° C. to 180° C., and the drying insulation time is 4 h to 7 h.

[0012] Based on the above, the modification step includes: modifying the SiC precursor diamond composite powder in a vacuum furnace at a temperature of 400° C. to 600° C. for a holding time of 3 h to 4 h.

[0013] Based on the above, the step of ball milling granulation includes:

[0014] The modified samples were ball-milled in a ball mill for 48 to 72 hours and then dried.

[0015] The dried ball-milled powder is mixed with ultrapure water to prepare a ceramic slurry with a viscosity of 150 MPa.s to 300 MPa.s, and then a temporary binder is added to the ceramic slurry. After mixing, a granulator is used to perform granulation treatment, wherein the added mass of the temporary binder accounts for 1% to 5% of the mass of the ceramic slurry.

[0016] The temporary adhesive may be one or more of PVA, PEG, dextrin, etc. with a mass fraction of 0.5% to 1%.

[0017] Based on the above, the sintering step includes:

[0018] The granulated particles are buried in sand and then sintered in a vacuum furnace or an atmosphere furnace at a sintering temperature of 1100°C to 1700°C for a holding time of 200min to 500min. After cooling, they are sorted to obtain agglomerated diamonds. The burying in sand treatment uses one or more materials such as SiC, diamond, BN, and alumina, and the added mass accounts for 25% to 50% of the mass of the granulated particles. The atmosphere can be an inert gas such as argon and helium.

[0019] The present invention also provides an agglomerated diamond, which is prepared by the preparation method described in claim 6. The agglomerated diamond comprises a ceramic binder and diamonds dispersed in the ceramic binder, wherein the ceramic binder is obtained by converting a SiC precursor during the diamond sintering process.

[0020] Based on the above, in the agglomerated diamond, the mass percentage of diamond is 70% to 90%.

[0021] The invention also provides an application of agglomerated diamonds, wherein the agglomerated diamonds are used as abrasives to grind SiC wafers.

[0022] The present invention has substantial characteristics and progress compared with the prior art. Specifically, the present invention provides agglomerated diamond and a preparation method and application thereof. SiC precursor and diamond are used as raw materials, and a dissolution and impregnation method is adopted to prepare SiC precursor diamond composite powder, and after modification, a spray granulation technology is adopted to prepare spherical agglomerated diamond. SiC precursor conversion ceramic is grown in situ on the diamond surface by sintering technology. As a result, a high-hardness binder is present in the agglomerated diamond, making the agglomerated diamond difficult to break during the grinding process, thereby improving the life and grinding efficiency of the abrasive grinding wheel prepared by the agglomerated diamond.

[0023] Furthermore, by controlling the particle size and content of diamond in the agglomerated diamond, the agglomerated diamond is spherical, and most of the particles have a good spherical morphology. The spherical agglomerated diamond wraps and bonds the diamond particles together through the glass phase, and a large number of diamond particles are exposed and semi-embedded on the surface, thereby ensuring that the exposed and semi-embedded diamond particles can play a grinding role during the abrasive machining of the workpiece, greatly increasing the number of grinding edges, effectively improving the grinding efficiency and reducing the surface roughness of the workpiece. At the same time, since the diamond particles are bonded together by the in-situ generated SiC phase, the structure also has good self-sharpening and impact resistance.

[0024] Furthermore, in the process of preparing agglomerated diamond, by performing modification treatment, the polycarbosilane can be thermally decomposed and transformed in its organizational morphology before balling and granulation, so that organic groups such as -H and -CH can be gradually removed in the modification step. At the same time, through the heating and cooling process of the modification step, the bubbles generated in the thermal decomposition process can be discharged in advance, effectively avoiding the generation of foaming bodies in the subsequent balling and sintering process, thereby improving the density and hardness of the material.

[0025] In addition, according to thermodynamic analysis, when granulation and sintering are carried out after modification, the microstructure phase undergoes further changes based on the structural components generated after the modified pyrolysis, rather than requiring transformation from polycarbosilane, thereby reducing the difficulty of structural transformation, reducing the entropy that needs to be overcome for material structural transformation, and improving the bonding quality between materials, thereby promoting the subsequent granulation and sintering process and structural changes, enabling it to be completely cracked and transformed into amorphous SiC, and then the amorphous SiC is transformed into crystalline β-SiC, ensuring that the agglomerated diamond has the advantages of high temperature resistance, high hardness, high strength, corrosion resistance, and oxidation resistance.

[0026] Therefore, the agglomerated diamond prepared by the preparation method provided by the present invention has high hardness and high wear resistance, and the processed wafer has excellent surface quality. Under the condition of the surface roughness of the same wafer, it has higher processing efficiency and abrasive service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 and Figure 2 This is a SEM image of agglomerated diamond provided in Example 1 of the present invention.

[0028] Figure 3 This is the EDS image of agglomerated diamond provided in Example 1 of the present invention.

[0029] Figure 4 is the XRD pattern of agglomerated diamond obtained at different sintering temperatures. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0031] Example 1

[0032] This embodiment provides a method for preparing agglomerated diamond, comprising the following steps:

[0033] Step 1: Weigh 30g of polycarbosilane or modified product and dissolve it in toluene, xylene, n-hexane, acetone and ethanol solvents, then weigh 70g of diamond with a median particle size of 1.5μm, and add the weighed diamond to the above solution and mix evenly; then place it in a 130℃ oil bath and stir and keep warm for 8h; finally place it in an oven and dry it at 180℃ for 7h.

[0034] Step 2: Modify the dried sample in a vacuum furnace at a temperature of 600°C and a holding time of 4 hours.

[0035] Step 3: ball-mill the modified sample in a planetary ball mill or a drum ball mill, and dry it after ball-milling for 72 hours.

[0036] Step 4: Mix the dried ball-milled powder with ultrapure water to prepare a ceramic slurry with a viscosity of 200 mPa.s, and then add 0.5% by mass of PVA, PEG, dextrin, etc. or more as a temporary binder to the ceramic slurry; wherein the amount of the temporary binder added is 1% of the mass of the ceramic slurry. After mixing evenly, use a centrifugal, spray or boiling granulator for granulation.

[0037] Step 5: The granulated particles are buried in sand, the type of sand is SiC, and the amount of sand selected is 30% of the mass of the granulated particles. They are then sintered in a vacuum furnace at a sintering temperature of 1600°C and a holding time of 200min to 500min. Finally, the cooled samples are sorted to separate the sand and granulated particles to obtain agglomerated diamonds.

[0038] This embodiment also provides agglomerated diamonds obtained by the preparation method.

[0039] Example 2

[0040] This embodiment provides a method for preparing agglomerated diamonds, which is different from Embodiment 1 mainly in that in this embodiment: the median particle size of diamonds in the raw material of agglomerated diamonds is 3.5 μm.

[0041] This embodiment also provides agglomerated diamonds obtained by the preparation method.

[0042] Example 3

[0043] This embodiment provides a method for preparing agglomerated diamonds, which is different from Embodiment 1 or Embodiment 2 mainly in that, in this embodiment: the mass of polycarbosilane or modified product is 10 g, and the mass of diamonds with a median particle size of 1.5 μm is 90 g.

[0044] This embodiment also provides agglomerated diamonds obtained by the preparation method.

[0045] Example 4

[0046] This embodiment provides a method for preparing agglomerated diamonds, which is different from Embodiment 1 or Embodiment 2 mainly in that, in this embodiment: the mass of polycarbosilane or its modified product is 20 g, and the mass of diamonds with a median particle size of 1.5 μm is 80 g.

[0047] This embodiment also provides agglomerated diamonds obtained by the preparation method.

[0048] Example 5

[0049] This embodiment provides an application of the agglomerated diamond prepared by Embodiment 1 or Embodiment 2 or Embodiment 3 or Embodiment 4, wherein the agglomerated diamond is used as an abrasive to grind SiC wafers.

[0050] Comparative Example 1

[0051] This comparative example 1 provides a method for preparing agglomerated diamond, comprising the following steps:

[0052] Step 1. First, weigh 70g of diamond with a median particle size of 1.5μm and 30g of a ceramic binder with a median particle size of 1.5μm respectively, add the weighed diamond and ceramic binder to 50g of deionized water and mix evenly, then add one or more dispersants such as sodium hexametaphosphate, sodium dodecylbenzenesulfonate, hexadecylammonium chloride, etc., the amount of dispersant added is 0.5% of the mass of diamond, stir evenly, and obtain a ceramic slurry.

[0053] Step 2: Add 0.5% by mass of one or more of PVA, PEG, dextrin, etc. as a temporary binder to the ceramic slurry, and the added amount is 1% of the ceramic slurry. After mixing evenly, use a centrifugal, spray or boiling granulator for granulation.

[0054] Step three, bury the granulated particles with sand. The type of sand is diamond. The added mass of the selected sand is between 30% of the mass of the granulated particles. Then, sintering is carried out in a muffle furnace. The sintering temperature is 700°C and the insulation time is 300 minutes. Finally, the cooled sample is sorted to separate the sand and granulated particles to obtain agglomerated diamonds.

[0055] Comparative Example 2

[0056] Comparative Example 2 provides a method for preparing agglomerated diamonds. The difference from Comparative Example 1 is that in this comparative example, the median particle size of the ceramic binder in the raw material of agglomerated diamonds is 1.5 μm, and the median particle size of diamonds is 3.5 μm.

[0057] Grinding SiC wafer test

[0058] Processing efficiency test: The agglomerated diamonds obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were weighed at a mass fraction of 1%, mixed with 500 ml of deionized water, and 1 g of carboxymethyl cellulose was added to prepare a polishing solution. The SiC wafer was ground using a double-end grinder, and the thickness of the sample before and after grinding was weighed to calculate the processing efficiency.

[0059] Workpiece surface roughness measurement method: Use white light interferometer to measure the surface roughness of the ground SiC wafer sample and average it. The specific test results are shown in Table 1 below.

[0060] Table 1 Effect of different agglomerated diamonds on grinding SiC wafers

[0061]

[0062] It can be seen from Table 1 that when the agglomerated diamonds prepared by Example 1 and Example 2 of the present invention are used to grind SiC wafers, the processing efficiency of the present invention is higher under the conditions of the surface roughness of the same wafer. At the same time, after testing, compared with Comparative Examples 1 and 2, the agglomerated diamonds prepared by the present invention also have the advantages of high hardness and high wear resistance, thereby improving the service life of the agglomerated diamonds when grinding SiC wafers.

[0063] At the same time, the microstructure and components of the agglomerated diamond prepared in the embodiment were tested, and the test results are as follows: Figure 1 , Figure 2 , Figure 3 and Figure 4 shown.

[0064] from Figure 1 It can be seen that the agglomerated diamonds prepared by the present invention are quasi-spherical, and most of the particles have a good spherical morphology, with a particle size of less than 50 μm, and very few large blocks of matter bonded together. It can also be clearly seen that the quasi-spherical agglomerated diamonds wrap and bond the diamond particles together through the glass phase, and a large number of diamond particles are exposed and semi-embedded on the surface. This ensures that during the processing of the workpiece by the abrasive, the multiple exposed and semi-embedded diamond particles can all play a role in grinding, greatly increasing the number of grinding edges, effectively improving the grinding efficiency and reducing the surface roughness of the workpiece. At the same time, since the diamond particles are bonded together by the in-situ generated SiC phase, the structure also has good self-sharpening and impact resistance.

[0065] from Figure 2 , Figure 3 and Figure 4It can be seen that the SiC phase exists in the agglomerated diamond tissue components prepared by the present invention, and the SiC phase is distributed in a wide area. This shows that the preparation process provided by the present invention can promote the thermal decomposition and tissue morphology transformation of polycarbosilane, and the generated silicon carbide can be wrapped on the surface of diamond particles and filled in the pores, thereby improving the density and hardness of the abrasive. At the same time, the β-SiC and α-SiC converted from polycarbosilane have good wettability with diamond particles and can effectively inhibit the graphitization of diamond particles.

[0066] More importantly, the present invention carries out a modification step before balling and granulation, and heats the SiC precursor diamond composite powder in a vacuum furnace at a temperature of 400°C to 600°C for 3h to 4h, so that the polycarbosilane can undergo thermal decomposition and organizational morphology transformation before balling and granulation, so that organic groups such as -H and -CH are gradually removed in the modification step.

[0067] At the same time, through the heating and cooling process of the modification step, the bubbles generated by the thermal decomposition process can be discharged in advance, effectively avoiding the generation of foaming bodies in the subsequent ball sintering process, thereby improving the density and hardness of the material.

[0068] In addition, according to thermodynamic analysis, when granulation and sintering are carried out after modification, the microstructure phase undergoes further changes based on the structural components generated after the modified pyrolysis, rather than requiring transformation from polycarbosilane, thereby reducing the difficulty of structural transformation, reducing the entropy that needs to be overcome for material structural transformation, and improving the bonding quality between materials, thereby promoting the subsequent granulation and sintering process and structural changes, enabling it to be completely cracked and transformed into amorphous SiC, and then the amorphous SiC is transformed into crystalline β-SiC, ensuring that the agglomerated diamond has the advantages of high temperature resistance, high hardness, high strength, corrosion resistance, and oxidation resistance.

[0069] That is, the present invention actually divides the thermal decomposition and organizational morphology transformation of polycarbosilane into two stages, prolonging the process of thermal decomposition and organizational morphology transformation, so that it can fully carry out thermal decomposition and organizational transformation.

[0070] In addition, after the SiC precursor diamond composite powder is modified, the wetting angle and solubility of polycarbosilane with water can be changed, making it more soluble in water, making it easier to granulate later, ensuring the morphology of the particles after granulation and the density of the particles during subsequent sintering.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for preparing agglomerated diamond, comprising the following steps: Preparation of composite powder: SiC precursor and diamond are used as raw materials, and SiC precursor diamond composite powder is prepared by dissolution impregnation method; Modification: Pre-sintering modification treatment is performed on SiC precursor diamond composite powder; Ball milling granulation: the modified composite powder is ball milled and then granulated; The granulated particles are sintered by embedding sand, and then sorted to obtain agglomerated diamonds.

2. The method for preparing agglomerated diamond according to claim 1, characterized in that: The steps of preparing the composite powder include: Polycarbosilane is dissolved in toluene, xylene, n-hexane, acetone and ethanol solvents, diamond with a median particle size of 0.25 μm to 3.5 μm is added to the solvent and placed in an oil bath for stirring and heat preservation, and then placed in an oven for drying to obtain SiC precursor diamond composite powder, wherein the mass percentage of diamond is 70% to 90% and the mass percentage of polycarbosilane is 10% to 30%.

3. The method for preparing agglomerated diamond according to claim 1 or 2, characterized in that: The modification step comprises: modifying the SiC precursor diamond composite powder in a vacuum furnace at a temperature of 400° C. to 600° C. for a heat preservation time of 3 h to 4 h.

4. The method for preparing agglomerated diamond according to claim 1, characterized in that: The step of ball milling granulation comprises: The modified SiC precursor diamond composite powder is ball-milled in a ball mill for 48 to 72 hours, and then dried; The dried ball-milled powder is mixed with ultrapure water to prepare a ceramic slurry with a viscosity of 150 mpa.s to 300 mpa.s, and then a temporary binder is added to the ceramic slurry. After mixing, a granulator is used to perform granulation treatment, wherein the added mass of the temporary binder accounts for 1% to 5% of the mass of the ceramic slurry.

5. The method for preparing agglomerated diamond according to claim 1, 2 or 4, characterized in that: The sintering step comprises: The granulated particles are buried in sand and then sintered in a vacuum or inert atmosphere at a sintering temperature of 1100°C to 1700°C for a holding time of 200 min to 500 min. After cooling, the particles are sorted to obtain agglomerated diamonds.

6. An agglomerated diamond, characterized in that: The agglomerated diamond is prepared by the preparation method according to any one of claims 1 to 5, and the agglomerated diamond comprises a ceramic binder and diamonds dispersed in the ceramic binder, wherein the ceramic binder is obtained by converting a SiC precursor during the diamond sintering process.

7. The agglomerated diamond according to claim 6, characterized in that: In the agglomerated diamond, the mass percentage of diamond is 70% to 90%.

8. An application of the agglomerated diamond according to claim 6 or 7, characterized in that: The agglomerated diamond is used as an abrasive to grind SiC wafers.

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