CN117945738B - Preparation method of heat-conducting insulating magnesium oxide for high-temperature-resistant heating tube - Google Patents
Preparation method of heat-conducting insulating magnesium oxide for high-temperature-resistant heating tube Download PDFInfo
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- CN117945738B CN117945738B CN202410348558.2A CN202410348558A CN117945738B CN 117945738 B CN117945738 B CN 117945738B CN 202410348558 A CN202410348558 A CN 202410348558A CN 117945738 B CN117945738 B CN 117945738B
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- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims abstract description 171
- 239000000395 magnesium oxide Substances 0.000 title claims abstract description 113
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 238000010438 heat treatment Methods 0.000 title claims abstract description 37
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 59
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 59
- 239000010703 silicon Substances 0.000 claims abstract description 59
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 46
- 239000000843 powder Substances 0.000 claims abstract description 43
- 238000002156 mixing Methods 0.000 claims abstract description 28
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 23
- 238000003723 Smelting Methods 0.000 claims abstract description 22
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 18
- 239000002904 solvent Substances 0.000 claims abstract description 15
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 230000032683 aging Effects 0.000 claims abstract description 6
- 125000002091 cationic group Chemical group 0.000 claims abstract description 6
- 238000001035 drying Methods 0.000 claims abstract description 6
- 238000001914 filtration Methods 0.000 claims abstract description 6
- 239000011347 resin Substances 0.000 claims abstract description 6
- 229920005989 resin Polymers 0.000 claims abstract description 6
- 239000002245 particle Substances 0.000 claims description 21
- 235000012239 silicon dioxide Nutrition 0.000 claims description 13
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 9
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 5
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims description 5
- 239000000292 calcium oxide Substances 0.000 claims description 5
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 5
- 239000011593 sulfur Substances 0.000 claims description 5
- 229910052717 sulfur Inorganic materials 0.000 claims description 5
- 239000004111 Potassium silicate Substances 0.000 claims description 3
- 239000004115 Sodium Silicate Substances 0.000 claims description 3
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 3
- PAZHGORSDKKUPI-UHFFFAOYSA-N lithium metasilicate Chemical compound [Li+].[Li+].[O-][Si]([O-])=O PAZHGORSDKKUPI-UHFFFAOYSA-N 0.000 claims description 3
- 229910052912 lithium silicate Inorganic materials 0.000 claims description 3
- 229910052913 potassium silicate Inorganic materials 0.000 claims description 3
- 235000019353 potassium silicate Nutrition 0.000 claims description 3
- NNHHDJVEYQHLHG-UHFFFAOYSA-N potassium silicate Chemical compound [K+].[K+].[O-][Si]([O-])=O NNHHDJVEYQHLHG-UHFFFAOYSA-N 0.000 claims description 3
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 3
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 3
- LFQCEHFDDXELDD-UHFFFAOYSA-N tetramethyl orthosilicate Chemical compound CO[Si](OC)(OC)OC LFQCEHFDDXELDD-UHFFFAOYSA-N 0.000 claims description 3
- ZQZCOBSUOFHDEE-UHFFFAOYSA-N tetrapropyl silicate Chemical compound CCCO[Si](OCCC)(OCCC)OCCC ZQZCOBSUOFHDEE-UHFFFAOYSA-N 0.000 claims description 3
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 abstract description 15
- 238000000576 coating method Methods 0.000 abstract description 15
- 230000008569 process Effects 0.000 abstract description 5
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 abstract description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 229910052863 mullite Inorganic materials 0.000 abstract description 2
- 238000005245 sintering Methods 0.000 abstract description 2
- 230000035882 stress Effects 0.000 abstract description 2
- 230000002194 synthesizing effect Effects 0.000 abstract description 2
- 238000004458 analytical method Methods 0.000 description 7
- 238000001354 calcination Methods 0.000 description 7
- 238000001514 detection method Methods 0.000 description 5
- 239000000945 filler Substances 0.000 description 4
- 238000000441 X-ray spectroscopy Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 3
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 2
- 238000006136 alcoholysis reaction Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910001120 nichrome Inorganic materials 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/03—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on magnesium oxide, calcium oxide or oxide mixtures derived from dolomite
- C04B35/04—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on magnesium oxide, calcium oxide or oxide mixtures derived from dolomite based on magnesium oxide
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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
- C04B35/628—Coating the powders or the macroscopic reinforcing agents
- C04B35/62802—Powder coating materials
- C04B35/62805—Oxide ceramics
- C04B35/62807—Silica or silicates
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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
- C04B35/628—Coating the powders or the macroscopic reinforcing agents
- C04B35/62886—Coating the powders or the macroscopic reinforcing agents by wet chemical techniques
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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
- C04B2235/30—Constituents and secondary phases not being of a fibrous nature
- C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3217—Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
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- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
- C04B2235/30—Constituents and secondary phases not being of a fibrous nature
- C04B2235/34—Non-metal oxides, non-metal mixed oxides, or salts thereof that form the non-metal oxides upon heating, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3418—Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
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- C04B2235/34—Non-metal oxides, non-metal mixed oxides, or salts thereof that form the non-metal oxides upon heating, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3427—Silicates other than clay, e.g. water glass
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- C04B2235/34—Non-metal oxides, non-metal mixed oxides, or salts thereof that form the non-metal oxides upon heating, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3427—Silicates other than clay, e.g. water glass
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- C04B2235/48—Organic compounds becoming part of a ceramic after heat treatment, e.g. carbonising phenol resins
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- General Chemical & Material Sciences (AREA)
- Silicon Compounds (AREA)
- Inorganic Insulating Materials (AREA)
Abstract
The invention discloses a preparation method of heat-conducting insulating magnesium oxide for a high-temperature-resistant heating tube, which belongs to the technical field of magnesium oxide production and comprises the following steps: mixing the electric smelting magnesium oxide, beta-Al 2O3 and the silicon micro powder to obtain a mixture; mixing the solution I containing the silicon source with cationic resin, and filtering to obtain solution II; mixing the solution II with silica sol and an alcohol solvent, and aging to obtain a solution III; mixing the mixture with the solution III, and drying to obtain modified fused magnesia powder; and roasting the modified fused magnesia powder to obtain the heat-conducting insulating magnesia for the high-temperature-resistant heating tube. According to the invention, the internal stress generated by volume shrinkage generated in the high-temperature sintering process of the fused magnesia is counteracted by volume expansion caused by synthesizing mullite under the high-temperature condition by using beta-Al 2O3 and the silica powder, so that the uniformity and the integrity of the silica coating on the surface of the heat-conducting insulating magnesia are improved.
Description
Technical Field
The invention belongs to the technical field of magnesium oxide production, and particularly relates to a preparation method of heat-conducting insulating magnesium oxide for a high-temperature-resistant heating tube.
Background
The heating tube mainly comprises a stainless steel cylindrical shell, a nichrome heating wire and a filler. The core of the heating tube is the filler, wherein the filler in the prior art is mainly magnesium oxide, firstly, the magnesium oxide has higher heat conduction performance, and the heat generated by the heating wire can be rapidly conducted to the outer wall of the heating tube, so that the heating tube can be rapidly heated and can maintain stable working temperature; meanwhile, the magnesium oxide has excellent insulating property, so that the electric breakdown between the heating wire and the heating tube shell can be effectively prevented, and the safe operation of the heating tube is ensured; finally, the magnesium oxide has better pressure resistance and hydrophobicity, can keep stable performance in a humid environment, and further improves the reliability and stability of the heating tube.
From the above, it is known that the overall performance of the heating tube is determined by the quality of the filler magnesium oxide, and thus the preparation method of magnesium oxide is of great importance. The existing magnesia is mainly prepared by roasting electric smelting magnesia, the pressure resistance, insulation and hydrophobicity of magnesia powder are the key for determining the quality of heating tube products, in order to improve the quality of the electric grade magnesia powder, the preparation method of magnesia is improved in the prior art, for example, the invention patent with the publication number of CN111233012B discloses the electric grade magnesia powder and the preparation method thereof, the invention covers a silicon dioxide network formed by alcoholysis of a silicon solution A outside magnesia by a sol method, and the electric grade magnesia powder is prepared after roasting, so as to improve the moisture resistance, the high temperature resistance and the durability of the electric grade magnesia powder. The sol method has the advantages of low cost, simple operation method and the like, but in the process of roasting magnesium oxide, the surface area is reduced along with the shrinkage of the volume of the magnesium oxide, so that the finally obtained silicon dioxide coating is difficult to be uniform and complete, and although the high-purity magnesium oxide is used in the invention, the preparation cost of the electrical grade magnesium oxide powder is also increased along with the improvement of the purity of the high-purity magnesium oxide, so that the invention aims to improve the preparation method of the heat-conducting insulating magnesium oxide for the high-temperature-resistant heating tube.
Disclosure of Invention
The invention aims to provide a preparation method of heat-conducting insulating magnesium oxide for a high-temperature-resistant heating tube, which aims to solve the problems in the background technology.
The aim of the invention can be achieved by the following technical scheme:
A preparation method of heat-conducting insulating magnesium oxide for a high-temperature-resistant heating tube comprises the following steps:
S1, mixing electric smelting magnesium oxide, beta-Al 2O3 and silicon micropowder to obtain a mixture;
S2, mixing the solution I containing the silicon source with cationic resin, and filtering to obtain a solution II;
s3, mixing the solution II with silica sol and an alcohol solvent, and aging to obtain a solution III;
S4, mixing the mixture with the solution III, and drying to obtain modified fused magnesia powder;
And S5, roasting the modified fused magnesia powder to obtain the heat-conducting insulating magnesia for the high-temperature-resistant heating tube.
Further, the median particle diameter of the fused magnesia in S1 is 100-250 mu m; the mass percentage of magnesium oxide in the electric smelting magnesium oxide is more than or equal to 95.0%, the mass percentage of calcium oxide is less than or equal to 0.5%, the mass percentage of silicon dioxide is less than or equal to 1.0%, the mass percentage of aluminum oxide is less than or equal to 0.5%, the mass percentage of carbon is less than or equal to 0.3%, and the mass percentage of sulfur is less than or equal to 0.3%.
Further, the median particle diameter of beta-Al 2O3 in S1 is 50-150 μm, and the purity is more than or equal to 99.0%.
Further, the median particle diameter of the silicon micropowder in S1 is 10-50 μm, and the purity is more than or equal to 97.0%.
Further, the median particle diameters of the fused magnesia, the beta-Al 2O3 and the silicon micropowder in the S1 are gradually decreased.
Further, the mass ratio of the electric smelting magnesium oxide to the beta-Al 2O3 to the silicon micropowder in the S1 is 45.5-60.0:2.2-3.2:1.
Further, the mass ratio of the electric smelting magnesium oxide to the beta-Al 2O3 to the silicon micropowder in the S1 is 50.0-52.5:2.5-2.7:1.
Further, the solution containing the silicon source in S2 includes an inorganic silicon solution and an organic silicon solution; the mass ratio of the inorganic silicon solution to the organic silicon solution is 1:0.1-5.0.
Further, the inorganic silicon solution is selected from one of potassium silicate, sodium silicate and lithium silicate.
Further, the organic silicon solution is selected from one of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate.
Further, the median particle diameter of the silica sol in the step S3 is 5-1000nm, and the mass percentage concentration of the silica sol is 1% -50%.
Further, the alcohol solvent in S3 is selected from one of methanol, ethanol and n-propanol.
Further, the volume ratio of the solution II to the silica sol to the alcohol solvent in the step S3 is 1:0.5-10:0.1-5.
Further, the mass ratio of the fused magnesia powder to the solution III in the step S4 is 1:0.01-1.
Further, the roasting temperature in S5 is 1600-1800 ℃ and the roasting time is 8-10h.
Further, the roasting temperature is 1650-1700 ℃.
The invention has the beneficial effects that:
According to the invention, a certain amount of beta-Al 2O3 and silicon micropowder auxiliary materials are added into the fused magnesia, so that the heat-conducting insulating magnesia for the high-temperature-resistant heating pipe is finally prepared, and the coverage rate (average value) of the silicon dioxide coating on the surface of the modified fused magnesia powder after calcination is 98.6% -99.4% through detection.
The invention utilizes the volume expansion caused by synthesizing mullite under the high temperature condition by beta-Al 2O3 and the silicon micropowder to offset the internal stress generated by volume contraction generated in the high temperature sintering process of the fused magnesia, and in order to improve the uniform integrity of the silicon dioxide coating on the surface of the heat-conducting insulating magnesia after the roasting, the dosage ratio of the fused magnesia, beta-Al 2O3 and the silicon micropowder needs to be strictly controlled; meanwhile, the addition of the silica powder is beneficial to improving the bonding performance of the silica coating and the heat-conducting insulating magnesium oxide surface in the subsequent sol method; finally, the invention realizes the uniformity of mixing the three by setting the electric smelting magnesia, the beta-Al 2O3 and the silicon micro powder with grain size grading, and is beneficial to further improving the uniformity and the integrity of the silicon dioxide coating.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1: a preparation method of heat-conducting insulating magnesium oxide for a high-temperature-resistant heating tube comprises the following steps:
S1, mixing electric smelting magnesium oxide, beta-Al 2O3 and silicon micropowder to obtain a mixture;
S2, mixing the solution I containing the silicon source with cationic resin, and filtering to obtain a solution II;
S3, mixing the solution II with silica sol and an alcohol solvent, and aging for 12 hours at room temperature to obtain a solution III;
s4, mixing the mixture with the solution III, and drying for 6 hours at 60 ℃ to obtain modified fused magnesia powder, wherein a silicon dioxide coating is formed on the surface of the modified fused magnesia powder;
S5, roasting the modified fused magnesia powder to obtain the heat-conducting insulating magnesia for the high-temperature-resistant heating tube, and carrying out energy dispersion X-ray spectroscopy (EDS) analysis and detection, wherein the coverage rate (average value) of the silica coating on the surface of the modified fused magnesia powder after calcination is 98.6%.
Wherein, the median particle diameter of the electric smelting magnesia in S1 is 100 mu m; the mass percentage of magnesium oxide in the electric smelting magnesium oxide is more than or equal to 95.0 percent, the mass percentage of calcium oxide is less than or equal to 0.5 percent, the mass percentage of silicon dioxide is less than or equal to 1.0 percent, the mass percentage of aluminum oxide is less than or equal to 0.5 percent, the mass percentage of carbon is less than or equal to 0.3 per mill, and the mass percentage of sulfur is less than or equal to 0.3 per mill.
Wherein, the median particle diameter of beta-Al 2O3 in S1 is 50 μm, and the purity is more than or equal to 99.0%.
Wherein, the median particle diameter of the silicon micropowder in S1 is 10 mu m, and the purity is more than or equal to 97.0 percent.
Wherein the mass ratio of the electric smelting magnesium oxide to the beta-Al 2O3 to the silicon micropowder in the S1 is 45.5:2.2:1.
The solution I containing a silicon source in S2 is formed by mixing an inorganic silicon solution and an organic silicon solution according to the mass ratio of 1:0.1, and specifically, the inorganic silicon solution is potassium silicate; the organosilicon solution is methyl orthosilicate.
Wherein, the median particle diameter of the silica sol in S3 is 5nm, and the mass percentage concentration of the silica sol is 1%.
Wherein the alcohol solvent in S3 is selected from methanol.
Wherein the volume ratio of the solution II to the silica sol to the alcohol solvent in the S3 is 1:0.5:0.1.
Wherein the mass ratio of the fused magnesia powder to the solution III in the step S4 is 1:0.01.
Wherein, the roasting temperature in S5 is 1600 ℃ and the roasting time is 10 hours.
Example 2: a preparation method of heat-conducting insulating magnesium oxide for a high-temperature-resistant heating tube comprises the following steps:
S1, mixing electric smelting magnesium oxide, beta-Al 2O3 and silicon micropowder to obtain a mixture;
S2, mixing the solution I containing the silicon source with cationic resin, and filtering to obtain a solution II;
S3, mixing the solution II with silica sol and an alcohol solvent, and aging for 12 hours at room temperature to obtain a solution III;
s4, mixing the mixture with the solution III, and drying for 6 hours at 60 ℃ to obtain modified fused magnesia powder, wherein a silicon dioxide coating is formed on the surface of the modified fused magnesia powder;
S5, roasting the modified fused magnesia powder to obtain the heat-conducting insulating magnesia for the high-temperature-resistant heating tube, and carrying out energy dispersion X-ray spectroscopy (EDS) analysis and detection, wherein the coverage rate (average value) of the silica coating on the surface of the modified fused magnesia powder after calcination is 99.4%.
Wherein, the median particle diameter of the electric smelting magnesium oxide in S1 is 200 mu m; the mass percentage of magnesium oxide in the electric smelting magnesium oxide is more than or equal to 95.0 percent, the mass percentage of calcium oxide is less than or equal to 0.5 percent, the mass percentage of silicon dioxide is less than or equal to 1.0 percent, the mass percentage of aluminum oxide is less than or equal to 0.5 percent, the mass percentage of carbon is less than or equal to 0.3 per mill, and the mass percentage of sulfur is less than or equal to 0.3 per mill.
Wherein, the median particle diameter of beta-Al 2O3 in S1 is 100 μm, and the purity is more than or equal to 99.0%.
Wherein, the median particle diameter of the silicon micropowder in S1 is 40 μm, and the purity is more than or equal to 97.0%.
Wherein the mass ratio of the electric smelting magnesium oxide to the beta-Al 2O3 to the silicon micro powder in the S1 is 50:3:1.
The solution I containing the silicon source in the S2 is formed by mixing an inorganic silicon solution and an organic silicon solution according to the mass ratio of 1:3, specifically, the inorganic silicon solution is sodium silicate, and the organic silicon solution is tetraethoxysilane.
Wherein, the median particle diameter of the silica sol in S3 is 200nm, and the mass percentage concentration of the silica sol is 30%.
Wherein, the alcohol solvent in S3 is selected from ethanol.
Wherein the volume ratio of the solution II to the silica sol to the alcohol solvent in the step S3 is 1:2:4.
Wherein the mass ratio of the fused magnesia powder to the solution III in the step S4 is 1:0.5.
Wherein, the roasting temperature in S5 is 1700 ℃, and the roasting time is 9h.
Example 3: a preparation method of heat-conducting insulating magnesium oxide for a high-temperature-resistant heating tube comprises the following steps:
S1, mixing electric smelting magnesium oxide, beta-Al 2O3 and silicon micropowder to obtain a mixture;
S2, mixing the solution I containing the silicon source with cationic resin, and filtering to obtain a solution II;
S3, mixing the solution II with silica sol and an alcohol solvent, and aging for 12 hours at room temperature to obtain a solution III;
s4, mixing the mixture with the solution III, and drying for 6 hours at 60 ℃ to obtain modified fused magnesia powder, wherein a silicon dioxide coating is formed on the surface of the modified fused magnesia powder;
s5, roasting the modified fused magnesia powder to obtain the heat-conducting insulating magnesia for the high-temperature-resistant heating tube, and carrying out energy dispersion X-ray spectroscopy (EDS) analysis and detection, wherein the coverage rate (average value) of the silica coating on the surface of the modified fused magnesia powder after calcination is 99.1%.
Wherein the median particle diameter of the fused magnesia in S1 is 250 mu m, the mass percent of the magnesia in the fused magnesia is more than or equal to 95.0 percent, the mass percent of the calcium oxide is less than or equal to 0.5 percent, the mass percent of the silicon dioxide is less than or equal to 1.0 percent, the mass percent of the aluminum oxide is less than or equal to 0.5 percent, the mass percent of the carbon is less than or equal to 0.3 per mill, and the mass percent of the sulfur is less than or equal to 0.3 per mill.
Wherein, the median particle diameter of the silicon micropowder in S1 is 50 μm, and the purity is more than or equal to 97.0%.
Wherein the mass ratio of the electric smelting magnesium oxide to the beta-Al 2O3 to the silicon micro powder in the S1 is 60:3.2:1.
The solution I containing the silicon source in the S2 is formed by mixing an inorganic silicon solution and an organic silicon solution according to a mass ratio of 1:5, specifically, the inorganic silicon solution is lithium silicate, and the organic silicon solution is propyl orthosilicate.
Wherein, the median particle diameter of the silica sol in S3 is 1000nm, and the mass percentage concentration of the silica sol is 50%.
Wherein the alcohol solvent in S3 is selected from n-propanol.
Wherein the volume ratio of the solution II to the silica sol to the alcohol solvent in the step S3 is 1:10:5.
Wherein the mass ratio of the fused magnesia powder to the solution III in the step S4 is 1:1.
Wherein, the roasting temperature in S5 is 1800 ℃ and the roasting time is 8 hours.
Comparative example 1
Referring to the preparation method of example 1 of the patent publication No. CN111233012B, an electrical grade magnesia powder was obtained, and the coverage (average value) of the silica coating on the surface of the electrical grade magnesia powder after calcination was 94.3% as detected by energy dispersive X-ray spectroscopy (EDS) analysis.
Comparative example 2
Referring to the preparation method of example 2 of the patent publication No. CN111233012B, an electrical grade magnesia powder is obtained, and the coverage (average value) of the silica coating on the surface of the electrical grade magnesia powder after calcination is 92.6% through analysis and detection of energy dispersive X-ray spectroscopy (EDS). X-ray photoelectron spectroscopy (XPS) analysis
Comparative example 3
Referring to the preparation method of example 3 of the invention patent publication No. CN111233012B, an electrical grade magnesia powder was obtained, and the coverage (average value) of the silica coating on the surface of the electrical grade magnesia powder after calcination was 92.1% as detected by energy dispersive X-ray spectroscopy (EDS) analysis.
It should be noted that in this document, terms such as "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
Claims (8)
1. The preparation method of the heat-conducting insulating magnesium oxide for the high-temperature-resistant heating tube is characterized by comprising the following steps of:
S1, mixing electric smelting magnesium oxide, beta-Al 2O3 and silicon micropowder to obtain a mixture;
S2, mixing the solution I containing the silicon source with cationic resin, and filtering to obtain a solution II;
s3, mixing the solution II with silica sol and an alcohol solvent, and aging to obtain a solution III;
S4, mixing the mixture with the solution III, and drying to obtain modified fused magnesia powder;
s5, roasting the modified fused magnesia powder to obtain the heat-conducting insulating magnesia for the high-temperature-resistant heating tube;
In S1, the median particle diameters of the electric smelting magnesium oxide, the beta-Al 2O3 and the silicon micro powder are gradually decreased;
the mass ratio of the electric smelting magnesium oxide to the beta-Al 2O3 to the silicon micro powder in the S1 is 45.5-60.0:2.2-3.2:1;
the median particle diameter of the electric smelting magnesium oxide in S1 is 100-250 mu m;
the median particle diameter of the beta-Al 2O3 in the S1 is 50-150 mu m;
the median particle diameter of the silicon micropowder in the step S1 is 10-50 mu m;
and S3, the median particle size of the silica sol is 5-1000nm.
2. The method for preparing the heat-conducting insulating magnesium oxide for the high-temperature-resistant heating tube, which is disclosed in claim 1, is characterized in that the mass percentage of magnesium oxide in the electric smelting magnesium oxide is more than or equal to 95.0%, the mass percentage of calcium oxide is less than or equal to 0.5%, the mass percentage of silicon dioxide is less than or equal to 1.0%, the mass percentage of aluminum oxide is less than or equal to 0.5%, the mass percentage of carbon is less than or equal to 0.3%, and the mass percentage of sulfur is less than or equal to 0.3%.
3. The method for preparing the heat-conducting insulating magnesium oxide for the high-temperature resistant heating tube, which is disclosed in claim 1, wherein the purity of beta-Al 2O3 in S1 is more than or equal to 99.0%; the purity of the silicon micropowder in S1 is more than or equal to 97.0 percent.
4. The method for preparing heat-conducting insulating magnesium oxide for high-temperature resistant heating tube according to claim 1, wherein the solution containing silicon source in S2 comprises an inorganic silicon solution and an organic silicon solution; the mass ratio of the inorganic silicon solution to the organic silicon solution is 1:0.1-5.0.
5. The method for preparing heat-conducting insulating magnesium oxide for high-temperature resistant heating tube according to claim 4, wherein the inorganic silicon solution is one selected from potassium silicate, sodium silicate and lithium silicate; the organic silicon solution is selected from one of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate.
6. The method for preparing heat-conducting insulating magnesium oxide for high-temperature resistant heating tube according to claim 1, wherein the alcohol solvent in S3 is one selected from methanol, ethanol and n-propanol.
7. The method for preparing heat-conducting insulating magnesium oxide for high-temperature resistant heating pipe according to claim 1, wherein the roasting temperature in S5 is 1600-1800 ℃ and the roasting time is 8-10h.
8. The method for preparing heat-conducting insulating magnesium oxide for high-temperature resistant heating tube according to claim 7, wherein the roasting temperature is 1650-1700 ℃.
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