CN113999019A - Preparation method of silicon nitride ceramic granulation powder - Google Patents
Preparation method of silicon nitride ceramic granulation powder Download PDFInfo
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- CN113999019A CN113999019A CN202111401328.0A CN202111401328A CN113999019A CN 113999019 A CN113999019 A CN 113999019A CN 202111401328 A CN202111401328 A CN 202111401328A CN 113999019 A CN113999019 A CN 113999019A
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- 239000000843 powder Substances 0.000 title claims abstract description 91
- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 54
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 54
- 238000005469 granulation Methods 0.000 title claims abstract description 41
- 230000003179 granulation Effects 0.000 title claims abstract description 41
- 239000000919 ceramic Substances 0.000 title claims abstract description 17
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- 239000002002 slurry Substances 0.000 claims abstract description 74
- 239000002202 Polyethylene glycol Substances 0.000 claims abstract description 53
- 239000004372 Polyvinyl alcohol Substances 0.000 claims abstract description 53
- 229920001223 polyethylene glycol Polymers 0.000 claims abstract description 53
- 229920002451 polyvinyl alcohol Polymers 0.000 claims abstract description 53
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 50
- 239000007921 spray Substances 0.000 claims abstract description 47
- 238000005245 sintering Methods 0.000 claims abstract description 41
- 238000002156 mixing Methods 0.000 claims abstract description 32
- 239000003292 glue Substances 0.000 claims abstract description 28
- 238000000227 grinding Methods 0.000 claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 24
- 239000002270 dispersing agent Substances 0.000 claims abstract description 14
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 6
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 15
- 239000000395 magnesium oxide Substances 0.000 claims description 15
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 15
- ZCUFMDLYAMJYST-UHFFFAOYSA-N thorium dioxide Chemical compound O=[Th]=O ZCUFMDLYAMJYST-UHFFFAOYSA-N 0.000 claims description 15
- 229910003452 thorium oxide Inorganic materials 0.000 claims description 15
- 239000007790 solid phase Substances 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 8
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims description 6
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 claims description 6
- 235000019982 sodium hexametaphosphate Nutrition 0.000 claims description 6
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 claims description 6
- 238000009987 spinning Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 229910000420 cerium oxide Inorganic materials 0.000 claims description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 3
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims description 3
- 229910001954 samarium oxide Inorganic materials 0.000 claims description 3
- 229940075630 samarium oxide Drugs 0.000 claims description 3
- FKTOIHSPIPYAPE-UHFFFAOYSA-N samarium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[Sm+3].[Sm+3] FKTOIHSPIPYAPE-UHFFFAOYSA-N 0.000 claims description 3
- 238000003756 stirring Methods 0.000 description 31
- 230000000052 comparative effect Effects 0.000 description 13
- 235000015895 biscuits Nutrition 0.000 description 12
- 239000007788 liquid Substances 0.000 description 6
- 238000003825 pressing Methods 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 3
- 229920002037 poly(vinyl butyral) polymer Polymers 0.000 description 3
- 238000001694 spray drying Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000001413 cellular effect Effects 0.000 description 2
- 238000005034 decoration Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 239000004014 plasticizer Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000009694 cold isostatic pressing Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 210000003743 erythrocyte Anatomy 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
- C04B35/62605—Treating the starting powders individually or as mixtures
- C04B35/62695—Granulation or pelletising
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
- C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
- C04B35/632—Organic additives
- C04B35/634—Polymers
- C04B35/63404—Polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
- C04B35/63416—Polyvinylalcohols [PVA]; Polyvinylacetates
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- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
- C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
- C04B2235/54—Particle size related information
- C04B2235/5418—Particle size related information expressed by the size of the particles or aggregates thereof
- C04B2235/5436—Particle size related information expressed by the size of the particles or aggregates thereof micrometer sized, i.e. from 1 to 100 micron
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- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
- C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
- C04B2235/54—Particle size related information
- C04B2235/5418—Particle size related information expressed by the size of the particles or aggregates thereof
- C04B2235/5445—Particle size related information expressed by the size of the particles or aggregates thereof submicron sized, i.e. from 0,1 to 1 micron
Abstract
The invention provides a preparation method of silicon nitride ceramic granulated powder, belonging to the technical field of silicon nitride ceramics. Grinding and mixing a sintering aid, water and silicon nitride raw powder to obtain first slurry; dissolving polyvinyl alcohol and polyethylene glycol into water to obtain a glue solution; the mass ratio of the polyvinyl alcohol to the polyethylene glycol is (0.16-0.20): 1; the total mass of the polyvinyl alcohol and the alcohol polyethylene glycol is 2-8% of the total mass of the sintering aid and the silicon nitride raw powder; mixing the first slurry, a glue solution and a dispersing agent to obtain a second slurry; performing spray granulation on the second slurry to obtain granulated powder; the inlet temperature of the spray granulation is 300-340 ℃. The method can improve the apparent density of the silicon nitride ceramic granulated powder to 0.92g/cm3The above.
Description
Technical Field
The invention relates to the technical field of silicon nitride ceramics, in particular to a preparation method of silicon nitride ceramic granulated powder.
Background
The silicon nitride ceramic material has the properties of high strength, small density, strong wear resistance, good corrosion resistance, high thermal shock resistance, good self-lubrication, good electrical insulation and the like, is a preferred material for producing various structural ceramic parts at present, still has huge development potential, and has wide application in the fields of aerospace, machinery, chemical industry and the like.
The density of the biscuit of the silicon nitride can be improved, so that the density of the sintered biscuit can be effectively increased, the porosity is reduced, the mechanical property of the blank is improved, the improvement of the biscuit density is greatly influenced by the apparent density of the granulated powder, and the higher apparent density can obtain the higher biscuit density under the same pressure under the common condition.
The preparation method of the granulation powder comprises a vacuum ball milling method, a rotary vibration sieve and double cone mixer method, a spray granulation method and the like. The traditional vacuum ball milling method for preparing the powder with high apparent density has the defects of complex equipment, high cost, long time consumption and the like; although the method of the rotary vibration sieve and the double-cone mixer can pack powder with various densities, the waste of the residual powder and the complexity of the operation process also make the method difficult to be applied in large scale in production. The spray granulation method is simple to operate, but the prepared ceramic powder has low apparent density.
Disclosure of Invention
The invention aims to provide a preparation method of silicon nitride ceramic granulated powder, which can improve the apparent density of the silicon nitride ceramic granulated powder.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of silicon nitride ceramic granulated powder, which comprises the following steps:
grinding and mixing a sintering aid, water and silicon nitride raw powder to obtain first slurry;
dissolving polyvinyl alcohol and polyethylene glycol into water to obtain a glue solution; the mass ratio of the polyvinyl alcohol to the polyethylene glycol is (0.16-0.20): 1; the total mass of the polyvinyl alcohol and the alcohol polyethylene glycol is 2-8% of the total mass of the sintering aid and the silicon nitride raw powder;
mixing the first slurry, a glue solution and a dispersing agent to obtain a second slurry;
performing spray granulation on the second slurry to obtain granulated powder; the inlet temperature of the spray granulation is 300-340 ℃.
Preferably, the mass of the sintering aid is 5-15% of the total mass of the sintering aid and the silicon nitride raw powder.
Preferably, the sintering aid comprises one or more of magnesium oxide, cerium oxide, aluminum oxide, samarium oxide, thorium oxide and lanthanum oxide.
Preferably, the solid contents of the first slurry and the second slurry are 40-50% independently.
Preferably, the dispersant comprises sodium hexametaphosphate.
Preferably, the dispersant is added in an amount such that the viscosity of the second slurry is 2500 to 3500mPa · s.
Preferably, the step of grinding and mixing the sintering aid, the water and the silicon nitride raw powder comprises the following steps: and carrying out first grinding and mixing on the sintering aid and part of water, and then adding the silicon nitride raw powder and the rest part of water to carry out second grinding and mixing.
Preferably, the particle size of the solid phase particles in the first slurry satisfies 0.8 μm < D50 < 1.5 μm.
Preferably, the pressure of the pump for spray granulation is 840-920 MPa, the aperture of the spray sheet is 0.8-1.0 mm, and the thickness of the spinning sheet is 2-3 mm.
Preferably, the dissolving of the polyvinyl alcohol and the polyethylene glycol into water comprises: polyethylene glycol is added into water, stirred for 0.5h at 50 ℃, and then added with polyvinyl alcohol and stirred for 2h at 50 ℃.
The invention provides a preparation method of silicon nitride ceramic granulated powder, which comprises the following steps: grinding and mixing a sintering aid, water and silicon nitride raw powder to obtain first slurry; dissolving polyvinyl alcohol and polyethylene glycol into water to obtain a glue solution; the mass ratio of the polyvinyl alcohol to the polyethylene glycol is (0.16-0.20): 1; the total mass of the polyvinyl alcohol and the alcohol polyethylene glycol is 2-8% of the total mass of the sintering aid and the silicon nitride raw powder; mixing the first slurry, a glue solution and a dispersing agent to obtain a second slurry; performing spray granulation on the second slurry to obtain granulated powder; the inlet temperature of the spray granulation is 300-340 ℃.
Polyvinyl alcohol (PVA) is an active binder and has high viscosity at a temperature higher than Tg (generally 75-85 ℃), and polyethylene glycol (PEG) serving as a plasticizer of the PVA can penetrate through the PVA to separate secondary bonds in a separation chain of the PVA, so that the deformability of the PVA is increased; the invention controls the mass ratio of PVA/PEG to be (0.16-0.20): 1, can make the shrink that the liquid drop produced when spray drying bigger, accumulational more closely knit between the powder, the import temperature of cooperation spray granulation can control the moisture volatilization speed of liquid in spray granulation process, forms the granulation powder of similar erythrocyte form to obtain higher apparent density.
The method can obtain the erythrocyte-shaped granulated powder with compact internal structure, and the powder in the granulated powder is more tightly packed although the middle of the granulated powder has larger holes, so that the loose density can be effectively improved to 0.92g/cm3Meanwhile, the holes in the middle of the granulated powder are beneficial to gas removal in the pressing process, and the biscuit cracks are reduced.
Detailed Description
The invention provides a preparation method of silicon nitride ceramic granulated powder, which comprises the following steps:
grinding and mixing a sintering aid, water and silicon nitride raw powder to obtain first slurry;
dissolving polyvinyl alcohol and polyethylene glycol into water to obtain a glue solution; the mass ratio of the polyvinyl alcohol to the polyethylene glycol is (0.16-0.20): 1; the total mass of the polyvinyl alcohol and the alcohol polyethylene glycol is 2-8% of the total mass of the sintering aid and the silicon nitride raw powder;
mixing the first slurry, a glue solution and a dispersing agent to obtain a second slurry;
performing spray granulation on the second slurry to obtain granulated powder; the inlet temperature of the spray granulation is 300-340 ℃.
In the present invention, the starting materials used are all commercially available products well known in the art, unless otherwise specified.
The method comprises the steps of grinding and mixing a sintering aid, water and silicon nitride raw powder to obtain first slurry.
In the invention, the sintering aid preferably comprises one or more of magnesium oxide, cerium oxide, aluminum oxide, samarium oxide, thorium oxide and lanthanum oxide, and when the sintering aid comprises a plurality of sintering aids, the proportion of each sintering aid is not specially required, and any proportion can be adopted. In the present invention, D50 of the sintering aid is preferably < 1 μm.
In the present invention, the silicon nitride raw powder preferably has a D50 of < 2 μm, an alpha phase mass content of more than 90%, and a specific surface area of more than 10m2The mass content of oxygen is preferably < 2.00%, the mass content of iron is preferably < 0.20%, and the mass content of carbon is preferably < 0.50%.
In the invention, the mass of the sintering aid is preferably 5-15%, more preferably 8-12%, and even more preferably 9-11% of the total mass of the sintering aid and the silicon nitride raw powder. In the present invention, the mass of the water is preferably 40 to 50% of the solid content of the first slurry.
In the invention, the grinding and mixing of the sintering aid, water and silicon nitride raw powder comprises: and carrying out first grinding and mixing on the sintering aid and part of water, and then adding the silicon nitride raw powder and the rest part of water to carry out second grinding and mixing. In the invention, the proportion of the part of water and the rest of water is not specially required, and the sintering aid and the silicon nitride raw powder can be uniformly dispersed. In the present invention, the grinding and mixing are preferably carried out in a roller mill. The invention has no special requirement on the specific conditions of the first grinding mixing and the second grinding mixing, and the grinding is carried out until the particle size of solid phase particles in the first slurry meets the requirement that the particle size is more than 0.8 mu m and less than D50 and less than 1.5 mu m. The invention adopts the step-by-step grinding, which is favorable for the sintering auxiliary agent to be uniformly dispersed in the silicon nitride slurry. The particle sizes of the sintering aid and the silicon nitride raw powder are small, false agglomeration is easy to form, and the sintering aid and the silicon nitride raw powder are scattered through grinding and mixing to obtain the first slurry with good dispersibility.
The invention dissolves polyvinyl alcohol and polyethylene glycol into water to obtain glue solution.
In the present invention, the molecular weight of the polyvinyl alcohol is preferably 20000; the molecular weight of the polyethylene glycol is preferably 20000.
In the invention, the mass ratio of the polyvinyl alcohol to the polyethylene glycol is (0.16-0.20): 1, preferably (0.17-0.19): 1, most preferably 0.18: 1; the total mass of the polyvinyl alcohol and the alcohol polyethylene glycol is 2-8%, preferably 3-7% and more preferably 4-6% of the total mass of the sintering aid and the silicon nitride raw powder.
In the present invention, the dissolving of the polyvinyl alcohol and the polyethylene glycol into water preferably includes: polyethylene glycol is added into water, stirred for 0.5h at 50 ℃, and then added with polyethylene glycol and stirred for 2h at 50 ℃. The present invention does not require any particular speed of agitation, and can employ agitation speeds well known in the art. In the invention, the addition amount of water in the glue solution is preferably such that the solid content of the second slurry obtained by mixing the first slurry and the glue solution reaches 40-50%.
In the invention, the polyvinyl alcohol is used as an active binder and has higher viscosity at the temperature higher than Tg, and polyethylene glycol (PEG) is used as a plasticizer of the PVA and can penetrate through the PVA to separate secondary bonds in a separation chain, so that the deformability of the PVA is increased; the invention controls the mass ratio of PVA/PEG to be (0.16-0.20): 1, the liquid drops can shrink more during spray drying, and the powder bodies are stacked more densely.
After obtaining the glue solution and the first slurry, the invention mixes the first slurry, the glue solution and the dispersant to obtain the second slurry.
In the present invention, the mixing preferably comprises: adding the first slurry into a stirring mill, stirring for 1h, then adding a glue solution, continuing stirring for 1h, and finally adding a dispersing agent. In the present invention, the dispersant is preferably added in an amount such that the viscosity of the second slurry is 2500 to 3500mPa · s. In the present invention, the temperature of the second slurry is preferably 25 to 35 ℃.
After the second slurry is obtained, the second slurry is subjected to spray granulation to obtain granulated powder.
In the present invention, the spray granulation is preferably performed in a spray granulation tower, and the spray granulation tower preferably employs a pressure type spray gun. In the invention, the inlet temperature of the spray granulation is 300-340 ℃, preferably 310-330 ℃, and more preferably 320 ℃. The pump pressure of the spray granulation is preferably 840-920 MPa, and more preferably 880 MPa; the aperture of the spray piece is preferably 0.8-1.0 mm, and more preferably 0.9 mm; the thickness of the rotary vane is preferably 2-3 mm, and more preferably 2.5 mm.
In the spray granulation process, small liquid drops formed by atomizing the second slurry through the nozzle of the spray gun fall after reaching a certain height, and moisture in the liquid drops volatilizes in the process and forms spheroidal granulation powder after drying. When the inlet temperature is higher than that of the invention, the liquid volatilizes at the highest speed to cause the water to be separated from the powder rapidly, the granulation powder is cracked due to rapid heating to form powder with poor sphericity, which is not beneficial to improving the apparent density. When the inlet temperature is lower than that of the present invention, the granulated powder does not have enough heat to rapidly shrink into a compact cellular shape, but forms a loose spherical granulated powder, which reduces the loose packing density.
The method can obtain the erythrocyte-shaped granulated powder with compact internal structure, and the powder in the granulated powder is more tightly packed although the middle of the granulated powder has larger holes, so that the loose density can be effectively improved to 0.92g/cm3Meanwhile, the holes in the middle of the granulated powder are beneficial to exhausting gas in the pressing process and reducing gasThe biscuit crack is less generated.
The following will explain the method for preparing the silicon nitride ceramic granulated powder of the present invention in detail with reference to the examples, but they should not be construed as limiting the scope of the present invention.
The silicon nitride raw powders used in the following examples and comparative examples were high-purity silicon nitride raw powders, D50 < 2 μm, alpha-phase content of more than 90% by mass, and specific surface area of > 10m2The mass content of oxygen is less than 2.00 percent, the mass content of iron is less than 0.20 percent, and the mass content of carbon is less than 0.50 percent.
Example 1
15kg of sintering aid (thorium oxide and magnesium oxide, the mass ratio of thorium oxide to magnesium oxide is 1: 4, and D50 is less than 1 mu m) and 15kg of water are added into a roller mill together for grinding and mixing for 6 hours, then 85kg of high-purity silicon nitride raw powder and 85kg of water are added and ground until the D50 is less than 0.8 and less than 1.5 mu m, and first slurry with good uniformity is prepared, wherein the solid phase content is 50%. Adding 2.54kg of polyethylene glycol (PEG, molecular weight 20000) into 20kg of water, stirring and dissolving at 50 ℃ for 0.5h, then adding 0.46kg of polyvinyl alcohol (PVB, molecular weight 200000), stirring and dissolving at 50 ℃ for 2h, and preparing uniform and consistent glue solution. Adding the prepared first slurry into a stirring mill, stirring for 1h, adding a glue solution, continuously stirring for 1h, adding sodium hexametaphosphate to control the viscosity of the slurry to be 3000 mPa.s, obtaining a second slurry with better dispersibility and fluidity, wherein the temperature of the second slurry is 30 ℃, a pressure type spray gun is adopted, the pressure of a feed pump is 880MPa, the aperture of a spray sheet is 0.9mm, the thickness of a rotary sheet is 2.5mm, the inlet temperature is 320 ℃, and granulating powder is obtained after spray granulation. The ratio of PVA to PEG mass was 0.18.
Example 2
15kg of sintering aid (thorium oxide and magnesium oxide, the mass ratio of thorium oxide to magnesium oxide is 1: 4, and D50 is less than 1 mu m) and 15kg of water are added into a roller mill together for grinding and mixing for 6 hours, then 85kg of high-purity silicon nitride raw powder and 85kg of water are added and ground until the D50 is less than 0.8 and less than 1.5 mu m, and first slurry with good uniformity is prepared, wherein the solid phase content is 50%. Adding 2.50kg of polyethylene glycol (PEG, molecular weight 6000) into 20kg of water, stirring and dissolving at 50 ℃ for 0.5h, then adding 0.50kg of polyvinyl alcohol (PVA, molecular weight 200000) at 50 ℃ and stirring and dissolving for 2h to prepare uniform and consistent glue solution. Adding the prepared first slurry into a stirring mill, stirring for 1h, adding a glue solution, continuously stirring for 1h, adding sodium hexametaphosphate to control the viscosity of the slurry to be 3000 mPa.s, and obtaining a second slurry with good dispersibility and fluidity, wherein the temperature of the second slurry is 30 ℃. A pressure type spray gun is adopted, the pressure of a feeding pump is 880MPa, the aperture of a spray sheet is 0.9mm, the thickness of a spinning sheet is 2.5mm, the inlet temperature is 320 ℃, and granulation powder is obtained after spray granulation. The ratio of PVA to PEG mass was 0.2.
Example 3
15kg of sintering aid (thorium oxide and magnesium oxide, the mass ratio of thorium oxide to magnesium oxide is 1: 4, and D50 is less than 1 mu m) and 15kg of water are added into a roller mill together for grinding and mixing for 6 hours, then 85kg of high-purity silicon nitride raw powder and 85kg of water are added and ground until the D50 is less than 0.8 and less than 1.5 mu m, and first slurry with good uniformity is prepared, wherein the solid phase content is 50%. Adding 2.58kg of polyethylene glycol (PEG, molecular weight 20000) into 20kg of water, stirring and dissolving at 50 ℃ for 0.5h, then adding 0.42kg of polyvinyl alcohol (PVA, molecular weight 200000) at 50 ℃ and stirring and dissolving for 2h to prepare uniform and consistent glue solution. Adding the prepared first slurry into a stirring mill, stirring for 1h, adding a glue solution, continuously stirring for 1h, adding sodium hexametaphosphate to control the viscosity of the slurry to be 3000 mPa.s, and obtaining a second slurry with good dispersibility and fluidity, wherein the temperature of the second slurry is 30 ℃. A pressure type spray gun is adopted, the pressure of a feeding pump is 880MPa, the aperture of a spray sheet is 0.9mm, the thickness of a spinning sheet is 2.5mm, the inlet temperature is 320 ℃, and granulation powder is obtained after spray granulation. The ratio of PVA to PEG mass was 0.16.
Comparative example 1
15kg of sintering aid (thorium oxide and magnesium oxide, the mass ratio of thorium oxide to magnesium oxide is 1: 4, and D50 is less than 1 mu m) and 15kg of water are added into a roller mill together for grinding and mixing for 6 hours, then 85kg of high-purity silicon nitride raw powder and 85kg of water are added and ground until the D50 is less than 0.8 and less than 1.5 mu m, and first slurry with good uniformity is prepared, wherein the solid phase content is 50%. Adding 2.60kg of polyethylene glycol (PEG, molecular weight 20000) into 20kg of water, stirring and dissolving at 50 ℃ for 0.5h, then adding 0.40kg of polyvinyl butyral (PVA, molecular weight 200000), stirring and dissolving at 50 ℃ for 2h, and preparing uniform glue solution. Adding the prepared first slurry into a stirring mill, stirring for 1h, adding a glue solution, continuously stirring for 1h, adding sodium hexametaphosphate to control the viscosity of the slurry to be 3000 mPa.s, and obtaining a second slurry with good dispersibility and fluidity, wherein the temperature of the second slurry is 30 ℃. A pressure type spray gun is adopted, the pressure of a feeding pump is 880MPa, the aperture of a spray sheet is 0.9mm, the thickness of a spinning sheet is 2.5mm, the inlet temperature is 320 ℃, and granulation powder is obtained after spray granulation. The ratio of PVA to PEG mass was 0.15.
Comparative example 2
15kg of sintering aid (thorium oxide and magnesium oxide, the mass ratio of thorium oxide to magnesium oxide is 1: 4, and D50 is less than 1 mu m) and 15kg of water are added into a roller mill together for grinding and mixing for 6 hours, then 85kg of high-purity silicon nitride raw powder and 85kg of water are added and ground until the D50 is less than 0.8 and less than 1.5 mu m, and first slurry with good uniformity is prepared, wherein the solid phase content is 50%. 2.45kg of polyethylene glycol (PEG, molecular weight 20000) is added into 20kg of water, the mixture is stirred and dissolved for 0.5h at 50 ℃, then 0.55kg of polyvinyl butyral (PVA, molecular weight 200000) is added, stirred and dissolved for 2h at 50 ℃, and uniform glue solution is prepared. Adding the prepared first slurry into a stirring mill, stirring for 1h, adding a glue solution, continuously stirring for 1h, adding a dispersing agent to control the viscosity of the slurry to be 3000 mPa.s to obtain a second slurry with good dispersibility and fluidity, wherein the temperature of the second slurry is 30 ℃, a pressure type spray gun is adopted, the pressure of a feed pump is 880MPa, the aperture of a spray sheet is 0.9mm, the thickness of a rotary sheet is 2.5mm, the inlet temperature is 320 ℃, and spray granulation is carried out to obtain granulation powder. The ratio of PVA to PEG mass was 0.22.
Comparative example 3
15kg of sintering aid (thorium oxide and magnesium oxide, the mass ratio of thorium oxide to magnesium oxide is 1: 4, and D50 is less than 1 mu m) and 15kg of water are added into a roller mill together for grinding and mixing for 6 hours, then 85kg of high-purity silicon nitride raw powder and 85kg of water are added and ground until the D50 is less than 0.8 and less than 1.5 mu m, and first slurry with good uniformity is prepared, wherein the solid phase content is 50%. Adding 2.54kg of polyethylene glycol (PEG, molecular weight 20000) into 20kg of water, stirring and dissolving at 50 ℃ for 0.5h, then adding 0.46kg of polyvinyl alcohol (PVA, molecular weight 200000) at 50 ℃ and stirring and dissolving for 2h to prepare uniform and consistent glue solution. Adding the prepared first slurry into a stirring mill, stirring for 1h, adding a glue solution, continuously stirring for 1h, adding a dispersing agent to control the viscosity of the slurry to be 3000 mPa.s to obtain a second slurry with good dispersibility and fluidity, wherein the temperature of the second slurry is 30 ℃, a pressure type spray gun is adopted, the pressure of a feed pump is 880MPa, the aperture of a spray sheet is 0.9mm, the thickness of a rotary sheet is 2.5mm, the inlet temperature is 280 ℃, and spray granulation is carried out to obtain granulation powder. The ratio of PVA to PEG mass was 0.18.
The bulk densities of the silicon nitride granulated powders of each of the examples and comparative examples were tested with reference to GB 1479-84, and each of the silicon nitride granulated powders was pressed into a biscuit, the bulk densities and the biscuit masses being shown in Table 1. Biscuit pressing conditions: biscuit pressing the prepared granulated powder by using a mould with a certain shape in a cold isostatic pressing way, wherein the pressing pressure is 300MPa, the pressure maintaining time is 60s, the pressure relief rate is controlled at 1MPa/s,
TABLE 1 apparent density and use of silicon nitride granulated powder in examples and comparative examples
| Examples | Apparent density g/cm3 | Green body cracking condition |
| Example 1 | 0.936 | Is free of |
| Example 2 | 0.929 | Is free of |
| Example 3 | 0.922 | Is free of |
| Comparative example 1 | 0.925 | Is provided with |
| Comparative example 2 | 0.912 | Is free of |
| Comparative example 3 | 0.885 | Is free of |
As can be seen from Table 1, the silicon nitride ceramic granulated powder with a low PVA/PEG ratio and a high inlet temperature selected by the invention has higher apparent density and no biscuit cracks than those of comparative examples 1-3; the reason is that although comparative example 1 has a high apparent density, the excessive addition of PEG causes a decrease in the rigidity of the binder at low temperatures and a decrease in the binding power, while comparative example 2 has a small addition of PEG and poor fluidity of PVA molecules, and the granulated powder is hard to shrink into a compact shell during spray drying, but forms a loose apple shape, and comparative example 3 has a low inlet temperature of the spray granulation tower and does not have sufficient heat to shrink into a compact cellular shape rapidly, but forms a loose spherical granulated powder.
In addition, when the inlet temperature is higher than 340 ℃, the granulated powder can be cracked due to rapid heating, and powder with poor sphericity is formed, which is not beneficial to the pressing of subsequent biscuit.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A preparation method of silicon nitride ceramic granulated powder is characterized by comprising the following steps:
grinding and mixing a sintering aid, water and silicon nitride raw powder to obtain first slurry;
dissolving polyvinyl alcohol and polyethylene glycol into water to obtain a glue solution; the mass ratio of the polyvinyl alcohol to the polyethylene glycol is (0.16-0.20): 1; the total mass of the polyvinyl alcohol and the alcohol polyethylene glycol is 2-8% of the total mass of the sintering aid and the silicon nitride raw powder;
mixing the first slurry, a glue solution and a dispersing agent to obtain a second slurry;
performing spray granulation on the second slurry to obtain granulated powder; the inlet temperature of the spray granulation is 300-340 ℃.
2. The production method according to claim 1, wherein the mass of the sintering aid is 5 to 15% of the total mass of the sintering aid and the silicon nitride raw powder.
3. The production method according to claim 1 or 2, wherein the sintering aid comprises one or more of magnesium oxide, cerium oxide, aluminum oxide, samarium oxide, thorium oxide, and lanthanum oxide.
4. The method according to claim 1, wherein the solids contents of the first slurry and the second slurry are independently 40 to 50%.
5. The method of claim 1, wherein the dispersant comprises sodium hexametaphosphate.
6. The production method according to claim 4 or 5, characterized in that the dispersant is added in an amount such that the viscosity of the second slurry is 2500 to 3500 mPa-s.
7. The method according to claim 1, wherein the step of grinding and mixing the sintering aid, the water, and the silicon nitride raw powder comprises: and carrying out first grinding and mixing on the sintering aid and part of water, and then adding the silicon nitride raw powder and the rest part of water to carry out second grinding and mixing.
8. The method according to claim 1 or 7, wherein the particle size of the solid phase particles in the first slurry satisfies 0.8 μm < D50 < 1.5 μm.
9. The method according to claim 1, wherein the pump pressure of the spray granulation is 840 to 920MPa, the hole diameter of the spray tablet is 0.8 to 1.0mm, and the thickness of the spinning tablet is 2 to 3 mm.
10. The method of claim 1, wherein dissolving the polyvinyl alcohol and the polyethylene glycol into water comprises: polyethylene glycol is added into water, stirred for 0.5h at 50 ℃, and then added with polyvinyl alcohol and stirred for 2h at 50 ℃.
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| WO2023088019A1 (en) * | 2021-11-19 | 2023-05-25 | 中材高新氮化物陶瓷有限公司 | Preparation method for silicon nitride ceramic granulated powder |
| CN116217243A (en) * | 2023-02-21 | 2023-06-06 | 华瓷聚力(厦门)新材料有限公司 | Silicon nitride powder granulating method |
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