Screening method of flaky or spherical nano SiC

Abstract

The invention discloses a screening method of flaky or spherical nano SiC, and belongs to the technical field of dispersion screening methods.The screening method comprises the steps that S1, SiC powder, a grinding medium, a ball milling tank, a mixed solvent, a dispersing agent and a modifying agent are prepared; s2, sequentially loading the weighed grinding medium and SiC powder into a ball milling tank; s3, preparing a mixed solvent, wherein the mixed solvent comprises benzene, alcohol and ketone; s4, dissolving a dispersing agent and a modifying agent into the mixed solvent; pouring the mixed solvent into a ball-milling tank, mixing the mixed solvent with a grinding medium and SiC powder, and setting the rotating speed of the ball-milling tank to form pre-dispersed slurry; s5, adding an adhesive, namely PVB (Polyvinyl Butyral) or DBP (Dibutyl Phthalate) or PVB sol, into the pre Setting the rotating speed of the ball-milling tank, determining the ball-milling time, and continuing ball-milling and mixing to form mixed slurry; s6, the final mixed slurry is sieved through a 40-mesh sieve and filtered, and the SiC slurry with uniform particles and uniform dispersion can be obtained after filtering is completed.

Description

Technical Field

[0001] The invention relates to the technical field of dispersed screening methods, in particular to a screening method for flaky or spherical nano SiC. Background Art

[0002] Due to their large specific surface area and surface energy, nanoparticles are prone to agglomeration during preparation and use, forming secondary particles, which weaken or eliminate the nanoparticle enhancement effect. Existing commercial SiC powders have poor sphericity and uneven particle size distribution.

[0003] The main defects of the existing technology are: commercial nano-SiC is mainly manufactured by chemical vapor deposition or high-temperature synthesis, and usually exhibits poor particle uniformity, large specific surface area, poor particle sphericity, and hard agglomeration and soft agglomeration, which brings certain difficulties to the dispersion process in the dry pressing spray granulation or casting precursor slurry process; the existing commercial SiC powder has slightly poor sphericity and uneven particle size distribution; due to the manufacturing process of nano-SiC, the existing nano-SiC contains some large particles of α-SiC, which also reduces the purity of β-SiC nano-powder. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a screening method for flaky or spherical nano-SiC to solve the problem raised in the background technology.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] A screening method for flaky or spherical nano-SiC, the screening method comprising:

[0007] S1: Weigh the raw materials according to the proportion, prepare SiC powder, grinding media, ball mill, mixed solvent, dispersant, modifier, wherein the ball mill is an alumina can;

[0008] S2: First, the weighed grinding media and SiC powder are loaded into the ball mill in sequence;

[0009] S3: preparing a mixed solvent, the mixed solvent comprising benzene, alcohol, and ketone, wherein benzene comprises toluene and xylene, alcohol comprises propanol, isopropanol, n-butanol, isobutanol, and sec-butanol, and ketone is butanone, the purity of the mixed solvent is above 99.5%, and the water content is below 0.1wt%;

[0010] S4: dissolving the dispersant and the modifier into the mixed solvent; pouring the mixed solvent into a ball mill to mix with the grinding medium and SiC powder, setting the speed of the ball mill, determining the dispersion time, pre-dispersing SiC to form a pre-dispersed slurry, in which the mixed solvent accounts for 40-90wt% of the mass of the pre-dispersed slurry, and the mass ratio of benzene, alcohol, and ketone to the pre-dispersed slurry is 5-60wt%: 5-40wt%: 0.4-10wt%;

[0011] S5: adding a binder: PVB or DBP or PVB sol to the above pre-dispersed slurry; setting the rotation speed of the ball mill, determining the ball milling time, and continuing the ball milling to form a mixed slurry;

[0012] S6: The final mixed slurry is filtered through a 40-mesh sieve to remove the grinding medium. The mixed slurry is fed into a pressure solvent, and the pressure is supplied by N2. The pressure is set to 0.2 MPa. The pressure vessel is connected to a filter equipped with a 2μm multi-layer stainless steel mesh. After the filtration is completed, SiC slurry with uniform particles and uniform dispersion can be obtained.

[0013] Preferably, the grinding medium is a high-purity alumina ball or a high-purity zirconia ball, and the particle size thereof is 0.5 to 5 μm.

[0014] Preferably, in step S4 and step S5, the rotation speed of the ball mill is 300 rpm to 1000 rpm, and the ball milling time is 0.5 h to 3 h.

[0015] Preferably, the dispersant is any one of castor oil, BYK-22552, polyvinyl pyrrolidone (PVP), TEGO-700, and KD-1, and the mass ratio of the dispersant to the pre-dispersed slurry is 0.2-5wt%.

[0016] Preferably, the modifier is used to modify the surface properties of nano-SiC powder, and the modifier is any one of polyether-modified siloxane, fluorine-modified acrylic polymer, polyethylene glycol, and n-octanol, and the mass ratio of the modifier to the pre-dispersed slurry is 0.5wt% to 5wt%.

[0017] Preferably, the adhesive is PVB with a molecular weight of 5000 to 50000, a hydroxyl content of 12 to 25 wt%, an acetate content of 1 to 4 wt%, a water content of less than 2 wt%, a glass transition temperature of 65 to 78°C, and a mass ratio of PVB added to the pre-dispersed slurry of 5 wt% to 12 wt%.

[0018] Preferably, the adhesive is a PVB sol, which includes PVB, a plasticizer and a solvent, wherein the solvent is a mixture of toluene, isopropyl alcohol and butanone, the solid content of the PVB sol is 20wt%, the plasticizer accounts for 5-15wt% of the sol, and the mass ratio of toluene, isopropyl alcohol and butanone in the solvent to the sol is 35wt%:25wt%:10wt%; the sol is allowed to reach a swollen state and is left to stand for more than 24 hours.

[0019] The above technical solution has the following beneficial effects:

[0020] The present application proposes a dry pressing or casting process that can stably disperse nano-SiC powder and match the existing commercial nano-sized silicon carbide powder as raw material to obtain a precursor slurry with uniform particles and stable dispersion. The preparation process is simple, the raw material composition is less complex, the cost is low, the SiC slurry has high stability, is not easy to settle, and has uniform particles, and effectively removes large particles of SiC in the SiC powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a particle morphology diagram of SiC powder in the prior art;

[0022] Figure 2 This is a particle morphology of SiC powder after dispersion by the method of this application. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] Example 1

[0025] A screening method for flaky or spherical nano-SiC, the screening method comprising:

[0026] S1: Weigh the raw materials according to the ratio, prepare SiC powder, grinding media, ball mill, mixed solvent, dispersant, and modifier, wherein the ball mill is an alumina can, and the grinding media is high-purity alumina balls or high-purity zirconia balls, and the particle size is 0.5-5 μm;

[0027] S2: First, the weighed grinding media and SiC powder are loaded into the ball mill in sequence;

[0028] S3: preparing a mixed solvent, the mixed solvent comprising benzene, alcohol, and ketone, wherein benzene comprises toluene and xylene, alcohol comprises propanol, isopropanol, n-butanol, isobutanol, and sec-butanol, and ketone is butanone, the purity of the mixed solvent is above 99.5%, and the water content is below 0.1wt%;

[0029] S4: dissolving the dispersant and the modifier into the mixed solvent; pouring the mixed solvent into the ball mill to mix with the grinding medium and SiC powder, setting the speed of the ball mill, and determining the dispersion time. Specifically, the speed of the ball mill is 300 rpm to 1000 rpm, preferably 400 to 800 rpm, and the ball milling time is 0.5 h to 3 h, and pre-dispersing SiC to form a pre-dispersed slurry. The particle morphology of the SiC powder at this time is as shown in FIG. Figure 2 As shown, in the pre-dispersed slurry, the mixed solvent accounts for 40-90wt% of the pre-dispersed slurry mass, and the mass ratio of benzene, alcohol, and ketone to the pre-dispersed slurry is 5-60wt%: 5-40wt%: 0.4-10wt%;

[0030] The dispersant is any one of castor oil, BYK-22552, polyvinyl pyrrolidone (PVP), TEGO-700, and KD-1, and the mass ratio of the dispersant to the pre-dispersed slurry is 0.2-5wt%;

[0031] The modifier is used to modify the surface properties of the nano-SiC powder. The modifier is any one of polyether-modified siloxane, fluorine-modified acrylic polymer, polyethylene glycol, and n-octanol. The mass ratio of the modifier to the pre-dispersed slurry is 0.5wt% to 5wt%.

[0032] S5: adding a binder: PVB or DBP or PVB sol to the above pre-dispersed slurry; setting the speed of the ball mill and determining the ball milling time, specifically, the speed of the ball mill is 300 rpm to 1000 rpm, the ball milling time is 0.5 h to 3 h, and continuing the ball milling to form a mixed slurry;

[0033] The binder is PVB, and its molecular weight is 5000-50000, preferably 10000-30000, the hydroxyl content in PVB is 12-25wt%, the acetate content is 1-4wt%, the water content is less than 2wt%, the glass transition temperature is 65-78°C, and the mass ratio of PVB added to the pre-dispersed slurry is 5wt%-12wt%;

[0034] The adhesive is a PVB sol, which includes PVB, a plasticizer and a solvent, wherein the solvent is a mixture of toluene, isopropyl alcohol and butanone, the solid content of the PVB sol is 20wt%, the plasticizer accounts for 5-15wt% of the sol, and the mass ratio of toluene, isopropyl alcohol and butanone in the solvent is 35wt%: 25wt%: 10wt% of the sol; the sol is allowed to swell and stand for more than 24 hours;

[0035] S6: The final mixed slurry is filtered through a 40-mesh sieve to remove the grinding medium, and the mixed slurry is fed into a pressure solvent, with N2 used for pressure supply, the pressure is set to 0.2 MPa, and the pressure vessel is connected to a filter with a 2 μm multi-layer stainless steel mesh. After the filtration is completed, SiC slurry with uniform particles and uniform dispersion can be obtained;

[0036] The present invention discloses a screening method for dispersing SiC powder by ball milling, which is suitable for preparing a precursor dispersion slurry of nano-alumina-silicon carbide composite ceramics by dry pressing or tape casting, so as to achieve uniform dispersion of SiC nanoparticles into a matrix structure or a main body;

[0037] refer to Figure 1 and Figure 2 , Figure 1 This is the particle morphology of a commercial SiC nanopowder. Figure 2 The morphology of SiC nanoparticles dispersed by the method of the present application is shown in Figure 1. By comparison, it is found that the SiC particles dispersed by the method of the present application are obvious and uniform;

[0038] The present application proposes a dry pressing or casting process that can stably disperse nano-SiC powder and match the existing commercial nano-sized silicon carbide powder as raw material to obtain a precursor slurry with uniform particles and stable dispersion. The preparation process is simple, the raw material composition is less complex, the cost is low, the SiC slurry has high stability, is not easy to settle, and has uniform particles, and effectively removes large particles of SiC in the SiC powder.

[0039] Example 2

[0040] A screening method for flaky or spherical nano-SiC, the screening method comprising:

[0041] S1: Weigh the raw materials according to the ratio, prepare SiC powder, grinding media, ball mill, mixed solvent, dispersant, and modifier, wherein the ball mill is an alumina can, and the grinding media is high-purity alumina balls or high-purity zirconia balls, and the particle size is 0.5-5 μm;

[0042] S2: First, the weighed grinding media and SiC powder are loaded into the ball mill in sequence;

[0043] S3: preparing a mixed solvent, wherein the mixed solvent includes benzene, alcohol, and ketone, wherein benzene includes toluene and xylene, alcohol includes propanol, isopropanol, n-butanol, isobutanol, and sec-butanol, and ketone is butanone. In other implementations of this embodiment, the benzene in the mixed solvent is toluene, and the alcohol is isopropanol, that is, the mixed solvent can be a mixture of toluene, isopropanol, and butanone, and the purity of the mixed solvent is 99.6%, and the water content is 0.09wt%;

[0044] S4: dissolving the dispersant and the modifier into the mixed solvent; pouring the mixed solvent into a ball mill to mix with the grinding medium and SiC powder, setting the speed of the ball mill, and determining the dispersion time. Specifically, the speed of the ball mill is 300 rpm. In other embodiments of this embodiment, the speed of the ball mill is 400 rpm, and the ball milling time is 0.5 h. Pre-dispersing SiC to form a pre-dispersed slurry, in which the mixed solvent accounts for 40 wt% of the mass of the pre-dispersed slurry, and the mass ratio of benzene, alcohol, and ketone to the pre-dispersed slurry is 5 wt%: 5 wt%: 0.4 wt%;

[0045] The dispersant is any one of castor oil, BYK-22552, polyvinyl pyrrolidone (PVP), TEGO-700, and KD-1, and the mass ratio of the dispersant to the pre-dispersed slurry is 0.2wt%;

[0046] The modifier is used to modify the surface properties of nano-SiC powder so as to be more suitable for dispersing and coating nano-sized silicon carbide. The modifier is any one of polyether-modified siloxane, fluorine-modified acrylic polymer, polyethylene glycol, and n-octanol. The mass ratio of the modifier to the pre-dispersed slurry is 0.5wt%;

[0047] S5: adding a binder to the pre-dispersed slurry, the binder being PVB or DBP or PVB sol; setting the rotation speed of the ball mill and determining the ball milling time, specifically, the rotation speed of the ball mill is 300 rpm. In other implementations of this embodiment, the rotation speed of the ball mill is 400 rpm, the ball milling time is 0.5 h, and continuing the ball milling to form a mixed slurry;

[0048] The binder is PVB, and its molecular weight is 5000. In other embodiments of this embodiment, the molecular weight of PVB is 10000, the hydroxyl content of PVB is 12wt%, the acetate content is 1wt%, the water content is 1.9wt%, the glass transition temperature is 65°C, and the mass ratio of PVB added to the pre-dispersed slurry is 5wt%;

[0049] In other implementations of this embodiment, the adhesive is a PVB sol, wherein the PVB sol includes PVB, a plasticizer and a solvent, wherein the solvent is a mixture of toluene, isopropanol and butanone, the solid content in the PVB sol is 20wt%, the plasticizer accounts for 5wt% of the sol, and the mass ratio of toluene, isopropanol and butanone in the solvent to the sol is 35wt%: 25wt%: 10wt%; the sol is allowed to swell and stand for 28h;

[0050] S6: The final mixed slurry is filtered through a 40-mesh sieve to remove the grinding medium. The mixed slurry is fed into a pressure solvent, and the pressure is supplied by N2. The pressure is set to 0.2 MPa. The pressure vessel is connected to a filter equipped with a 2μm multi-layer stainless steel mesh. After the filtration is completed, SiC slurry with uniform particles and uniform dispersion can be obtained.

[0051] Example 3

[0052] A screening method for flaky or spherical nano-SiC, the screening method comprising:

[0053] S1: Weigh the raw materials according to the proportion, prepare SiC powder, grinding media, ball mill, mixed solvent, dispersant, and modifier, wherein the ball mill is an alumina can, and the grinding media is high-purity alumina balls or high-purity zirconia balls with a particle size of 5 μm;

[0054] S2: First, the weighed grinding media and SiC powder are loaded into the ball mill in sequence;

[0055] S3: preparing a mixed solvent, the mixed solvent comprising benzene, alcohol, and ketone, wherein benzene comprises toluene and xylene, alcohol comprises propanol, isopropanol, n-butanol, isobutanol, and sec-butanol, and ketone is butanone, the purity of the mixed solvent is 99.7%, and the water content is 0.08wt%;

[0056] S4: dissolving the dispersant and the modifier into the mixed solvent; pouring the mixed solvent into a ball mill to mix with the grinding medium and SiC powder, setting the speed of the ball mill, and determining the dispersion time. Specifically, the speed of the ball mill is 1000 rpm. In other embodiments of this embodiment, the speed of the ball mill is 800 rpm, and the ball milling time is 3 hours. Pre-dispersing SiC to form a pre-dispersed slurry, in which the mixed solvent accounts for 90 wt% of the mass of the pre-dispersed slurry, and the mass ratio of benzene, alcohol, and ketone to the pre-dispersed slurry is 60 wt%: 40 wt%: 10 wt%;

[0057] The dispersant is any one of castor oil, BYK-22552, polyvinyl pyrrolidone (PVP), TEGO-700, and KD-1, and the mass ratio of the dispersant to the pre-dispersed slurry is 5wt%;

[0058] The modifier is used to modify the surface properties of the nano-SiC powder, and the modifier is any one of polyether-modified siloxane, fluorine-modified acrylic polymer, polyethylene glycol, and n-octanol, and the mass ratio of the modifier to the pre-dispersed slurry is 5wt%;

[0059] S5: adding a binder: PVB or DBP or PVB sol to the pre-dispersed slurry; setting the speed of the ball mill and determining the ball milling time. Specifically, the speed of the ball mill is 1000 rpm. In other implementations of this embodiment, the speed of the ball mill is 800 rpm, the ball milling time is 3 hours, and the ball milling is continued to form a mixed slurry;

[0060] The binder is PVB, and its molecular weight is 50000. In other embodiments of this embodiment, the molecular weight of PVB is 30000, the hydroxyl content in PVB is 25wt%, the acetate content is 4wt%, the water content is less than 2wt%, the glass transition temperature is 78°C, and the mass ratio of PVB added to the pre-dispersed slurry is 12wt%;

[0061] In other implementations of this embodiment, the adhesive may be a PVB sol, the PVB sol comprising PVB, a plasticizer and a solvent, wherein the solvent is a mixture of toluene, isopropanol and butanone, the solid content of the PVB sol is 20wt%, the plasticizer accounts for 15wt% of the sol, and the mass ratio of toluene, isopropanol and butanone in the solvent to the sol is 35wt%: 25wt%: 10wt%; the sol is allowed to swell and stand for 30h;

[0062] S6: The final mixed slurry is filtered through a 40-mesh sieve to remove the grinding medium. The mixed slurry is fed into a pressure solvent, and the pressure is supplied by N2. The pressure is set to 0.2 MPa. The pressure vessel is connected to a filter equipped with a 2μm multi-layer stainless steel mesh. After the filtration is completed, SiC slurry with uniform particles and uniform dispersion can be obtained.

[0063] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A method for screening flaky or spherical nano-SiC, characterized in that: The screening method comprises: S1: Weigh the raw materials according to the proportion, prepare SiC powder, grinding media, ball mill, mixed solvent, dispersant, modifier, wherein the ball mill is an alumina can; S2: First, the weighed grinding media and SiC powder are loaded into the ball mill in sequence; S3: preparing a mixed solvent, the mixed solvent comprising benzene, alcohol, and ketone, wherein benzene comprises toluene and xylene, alcohol comprises propanol, isopropanol, n-butanol, isobutanol, and sec-butanol, and ketone is butanone, the purity of the mixed solvent is above 99.5%, and the water content is below 0.1wt%; S4: dissolving the dispersant and the modifier into the mixed solvent; pouring the mixed solvent into a ball mill to mix with the grinding medium and SiC powder, setting the speed of the ball mill, determining the dispersion time, pre-dispersing SiC to form a pre-dispersed slurry, in which the mixed solvent accounts for 40-90wt% of the mass of the pre-dispersed slurry, and the mass ratio of benzene, alcohol, and ketone to the pre-dispersed slurry is 5-60wt%: 5-40wt%: 0.4-10wt%; S5: adding a binder: PVB or DBP or PVB sol to the above pre-dispersed slurry; setting the rotation speed of the ball mill, determining the ball milling time, and continuing the ball milling to form a mixed slurry; S6: The final mixed slurry is filtered through a 40-mesh sieve to remove the grinding medium. The mixed slurry is fed into a pressure solvent, and the pressure is supplied by N2. The pressure is set to 0.2 MPa. The pressure vessel is connected to a filter equipped with a 2μm multi-layer stainless steel mesh. After the filtration is completed, SiC slurry with uniform particles and uniform dispersion can be obtained.

2. The method for screening flaky or spherical nano-SiC according to claim 1, characterized in that: The grinding medium is a high-purity alumina ball or a high-purity zirconia ball, and the particle size thereof is 0.5 to 5 μm.

3. The method for screening flaky or spherical nano-SiC according to claim 1, characterized in that: In the step S4 and the step S5, the rotation speed of the ball mill is 300 rpm to 1000 rpm, and the ball milling time is 0.5 h to 3 h.

4. The method for screening flaky or spherical nano-SiC according to claim 1, characterized in that: The dispersant is any one of castor oil, BYK-22552, polyvinyl pyrrolidone (PVP), TEGO-700 and KD-1, and the mass ratio of the dispersant to the pre-dispersed slurry is 0.2-5wt%.

5. The method for screening flaky or spherical nano-SiC according to claim 1, characterized in that: The modifier is used to modify the surface properties of nano-SiC powder. The modifier is any one of polyether-modified siloxane, fluorine-modified acrylic polymer, polyethylene glycol, and n-octanol. The mass ratio of the modifier to the pre-dispersed slurry is 0.5wt% to 5wt%.

6. The method for screening flaky or spherical nano-SiC according to claim 1, characterized in that: The adhesive is PVB, with a molecular weight of 5000-50000, a hydroxyl content of 12-25wt%, an acetate content of 1-4wt%, a water content of less than 2wt%, a glass transition temperature of 65-78°C, and a mass ratio of PVB added to the pre-dispersed slurry of 5wt%-12wt%.

7. The method for screening flaky or spherical nano-SiC according to claim 1, characterized in that: The adhesive is a PVB sol, which includes PVB, a plasticizer and a solvent, wherein the solvent is a mixture of toluene, isopropyl alcohol and butanone, the solid content of the PVB sol is 20wt%, the plasticizer accounts for 5-15wt% of the sol, and the mass ratio of toluene, isopropyl alcohol and butanone in the solvent is 35wt%:25wt%:10wt% of the sol; the sol is allowed to reach a swollen state and is left to stand for more than 24 hours.

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