CN117418312A - Large single crystal spheroid alpha alumina and preparation method thereof - Google Patents
Large single crystal spheroid alpha alumina and preparation method thereof Download PDFInfo
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- CN117418312A CN117418312A CN202311635048.5A CN202311635048A CN117418312A CN 117418312 A CN117418312 A CN 117418312A CN 202311635048 A CN202311635048 A CN 202311635048A CN 117418312 A CN117418312 A CN 117418312A
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- alumina
- alpha alumina
- single crystal
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims abstract description 117
- 239000013078 crystal Substances 0.000 title claims description 43
- 238000002360 preparation method Methods 0.000 title abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 68
- 239000002994 raw material Substances 0.000 claims abstract description 26
- 238000004321 preservation Methods 0.000 claims abstract description 24
- 238000000034 method Methods 0.000 claims abstract description 20
- 239000012752 auxiliary agent Substances 0.000 claims abstract description 17
- 238000005245 sintering Methods 0.000 claims abstract description 16
- 239000000463 material Substances 0.000 claims abstract description 15
- 238000001354 calcination Methods 0.000 claims abstract description 14
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims abstract description 13
- 239000011734 sodium Substances 0.000 claims abstract description 13
- 229910052708 sodium Inorganic materials 0.000 claims abstract description 13
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 12
- 230000008859 change Effects 0.000 claims abstract description 11
- 238000004519 manufacturing process Methods 0.000 claims abstract description 11
- 239000003381 stabilizer Substances 0.000 claims abstract description 11
- 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 20
- 239000000203 mixture Substances 0.000 claims description 20
- 230000000630 rising effect Effects 0.000 claims description 19
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 18
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 claims description 18
- 238000005406 washing Methods 0.000 claims description 13
- 229910052810 boron oxide Inorganic materials 0.000 claims description 9
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 claims description 9
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 8
- 239000002253 acid Substances 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 229910000420 cerium oxide Inorganic materials 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 5
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims description 5
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 4
- 235000019270 ammonium chloride Nutrition 0.000 claims description 4
- WDIHJSXYQDMJHN-UHFFFAOYSA-L barium chloride Chemical compound [Cl-].[Cl-].[Ba+2] WDIHJSXYQDMJHN-UHFFFAOYSA-L 0.000 claims description 4
- 229910001626 barium chloride Inorganic materials 0.000 claims description 4
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 4
- 239000004327 boric acid Substances 0.000 claims description 4
- 239000001110 calcium chloride Substances 0.000 claims description 4
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 2
- 239000010431 corundum Substances 0.000 claims description 2
- 229910052593 corundum Inorganic materials 0.000 claims description 2
- 238000001035 drying Methods 0.000 claims description 2
- 239000007952 growth promoter Substances 0.000 claims description 2
- 230000001939 inductive effect Effects 0.000 claims description 2
- 229910017604 nitric acid Inorganic materials 0.000 claims description 2
- 239000002245 particle Substances 0.000 abstract description 33
- 230000008569 process Effects 0.000 abstract description 15
- 238000009826 distribution Methods 0.000 abstract description 14
- 239000000945 filler Substances 0.000 abstract description 7
- 238000010521 absorption reaction Methods 0.000 abstract description 4
- 230000004048 modification Effects 0.000 abstract description 3
- 238000012986 modification Methods 0.000 abstract description 3
- 238000010304 firing Methods 0.000 abstract 1
- 239000000047 product Substances 0.000 description 35
- 238000006243 chemical reaction Methods 0.000 description 18
- 230000000052 comparative effect Effects 0.000 description 17
- 238000007789 sealing Methods 0.000 description 11
- 230000001965 increasing effect Effects 0.000 description 8
- 239000003054 catalyst Substances 0.000 description 4
- 239000003822 epoxy resin Substances 0.000 description 4
- 239000004519 grease Substances 0.000 description 4
- 229920000647 polyepoxide Polymers 0.000 description 4
- 229920001296 polysiloxane Polymers 0.000 description 4
- 238000012546 transfer Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000012798 spherical particle Substances 0.000 description 3
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000011231 conductive filler Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000008213 purified water Substances 0.000 description 2
- 102220043159 rs587780996 Human genes 0.000 description 2
- 230000002195 synergetic effect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000002390 adhesive tape Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- VTYYLEPIZMXCLO-UHFFFAOYSA-L calcium carbonate Substances [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- -1 calcium carbonate compound Chemical class 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000009643 growth defect Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000010902 jet-milling Methods 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000012782 phase change material Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 239000000565 sealant Substances 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229920002379 silicone rubber Polymers 0.000 description 1
- 239000004945 silicone rubber Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
- C30B29/20—Aluminium oxides
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B1/00—Single-crystal growth directly from the solid state
- C30B1/10—Single-crystal growth directly from the solid state by solid state reactions or multi-phase diffusion
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/60—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape characterised by shape
- C30B29/66—Crystals of complex geometrical shape, e.g. tubes, cylinders
Abstract
The invention belongs to the technical field of inorganic nonmetallic materials, and particularly relates to large monocrystal spheroid alpha alumina and a preparation method thereof, wherein the alpha alumina is formed by calcining an alumina-containing raw material, a sodium removing agent, an induced phase change growth auxiliary agent and a stabilizer by adopting a three-stage heating and heat preservation strategy; the large monocrystalline spherical alpha alumina prepared by the invention has the advantages of particle size D50 of more than or equal to 25 mu m, small specific surface area, low oil absorption value, extremely narrow particle size distribution, good dispersibility and wettability, high addition fraction and excellent comprehensive performance, can be used for preparing high-quality filler of high-heat-conductivity interface materials, and can be used for preparing high-heat-conductivity products by singly using the large monocrystalline spherical alpha alumina. According to the invention, by setting reasonable temperature rise and heat preservation time, the intermediate sintering is not required to be taken out for modification, and the high-performance product can be prepared by one-step firing, so that the process flow is simplified, the production cost is reduced, and the method is easy to industrialize.
Description
[ field of technology ]
The invention belongs to the technical field of inorganic nonmetallic materials, and particularly relates to a large monocrystal spherical alpha alumina and a preparation method thereof.
[ background Art ]
In recent years, industries such as 5G communication, photovoltaics, new energy and the like rapidly develop, the chip size of electronic products is smaller and smaller, the power is larger and larger, the heat flux density is continuously increased, and the requirements on heat dissipation capacity are stricter and stricter. The heat dissipation of the chip is conducted by means of a heat conduction interface material between the heating part and the shell, and the heat conduction coefficient of the heat conduction interface material is a key index. The heat-conducting interface material is prepared by adding heat-conducting filler into organic matrixes such as silicone grease, epoxy resin and the like to prepare heat-conducting silicone grease, heat-conducting gaskets, heat-conducting gel, heat-conducting adhesive tapes, heat-conducting pouring sealant, heat-conducting phase-change materials and the like. Because the heat conductivity of silicone grease and epoxy resin is very low (0.1-0.3W/m.K), fillers with high heat conductivity and good insulation and corrosion resistance are generally required to be added. Common thermally conductive fillers include oxides (alumina, magnesia, zinc oxide, silica), nitrides (aluminum nitride, boron nitride), and carbon materials (diamond, graphite, etc.). Wherein, the alumina occupies a larger specific gravity in the heat conductive filler due to high cost performance, higher heat conductivity coefficient (30W/m.K), acid and alkali corrosion resistance and good dielectric insulation performance.
It is currently widely accepted that heat transfer in materials follows phonon transfer theory, i.e., filler particles contact each other in an organic matrix material to form innumerable chains or networks of conductive networks, and that heating of the particles causes lattice vibrations to generate phonons and transfer between the particles. The crystal structure, purity, particle size distribution, filling quantity, morphology and the like of the filler all have influence on the formation of the heat conduction network. The spherical alumina is a heat-conducting alumina powder which is mature in application at present and is generally prepared by a melt injection method, and because the melting phase transition time is extremely short, the product has low alpha phase conversion rate and low true density, cracks exist on the surface of spherical particles, hollowness exist in the interior of the spherical particles, the filling quantity of the spherical particles in an organic matrix is influenced, and the formed heat-conducting passages are fewer, so that the spherical alumina has the limitation in application in products requiring higher heat conductivity coefficients. And the production cost is higher and the yield is lower.
The large single crystal alumina, generally referred to as median particle diameter D50 > 20 μm, has been studied to show that by adding mineralizer to sinter at 1500 deg.C, large single crystal alpha alumina of about 20 μm can be prepared, but because of the difference in radial and axial production rates in the growth process of alpha alumina crystal, the morphology is mostly flaky, the viscosity increases in silicone grease or epoxy resin, the addition fraction is affected, and the thermal conductivity of the product is not high.
Patent CN113213513A discloses a preparation method of large single crystal alpha-alumina, which uses gamma alumina as raw material, and prepares the large single crystal alpha-alumina with median grain diameter D50 of 2-6 μm after high temperature sintering and jet milling by adding boric acid and calcium carbonate compound mineralizer, and the single crystal size is smaller, which can not meet the demand of heat conduction interface material for products with grain diameter larger than 25 μm.
The preparation method of the ceramic membrane support of the patent CN105565785A uses aluminum hydroxide as a raw material and fluoride and other composite mineralizers as additives, adopts a three-stage sintering process, and the maximum sintering temperature is more than or equal to 1650 ℃, so that the ceramic membrane support which is formed by spherical alumina and has the median particle diameter of more than 20 mu m is prepared.
The patent CN114751435A discloses a large primary crystal low sodium sphere-like alpha-alumina powder and a preparation method thereof, wherein industrial alumina is used as a raw material, fluoride, chloride and oxide compound mineralizer is adopted, two-stage sintering is adopted, the sphere-like alumina with the median particle diameter of 20-30 mu m is prepared, the adding proportion of fluorine-containing mineralizer is more than 5%, the environment is polluted, the energy consumption is higher, and the preparation process is more complex.
In summary, the prior art has the following problems: (1) the adoption of the multi-stage sintering process has the advantages of complex flow, higher energy consumption and higher production cost, and is not beneficial to industrialized mass production; (2) the fluorine-containing mineralizer is used as the sintering aid, and the volatilized product not only pollutes the environment, but also can corrode kiln equipment and kiln furniture, thereby shortening the service life of the equipment and increasing the kiln furniture loss; (3) the different action mechanisms of various mineralizers cannot be deeply researched, the synergistic effect of the composite mineralizers is simply exerted, and the stability of product indexes cannot be ensured; (4) the grain diameter of the quasi-spherical alpha alumina produced by most processes is generally less than 25 mu m, and the limit of the growth size of primary crystals is not broken through.
In conclusion, how to find a spherical high-heat-conductivity alumina which is clean, environment-friendly, green, low-carbon, simple in process, high in purity, high in alpha phase conversion rate, and high in median particle diameter D50 more than or equal to 25 mu m has important significance.
[ invention ]
The invention aims to provide large monocrystal spherical alpha alumina with median particle diameter D50 more than or equal to 25 mu m and concentrated particle size distribution and a preparation method thereof, wherein the preparation method is clean and environment-friendly and has simple technical process.
Based on the purposes, the application adopts the following technical scheme:
the first aspect of the invention provides large single crystal spherical alpha alumina, which is formed by calcining an alumina-containing raw material, a sodium removing agent, an induced phase change growth auxiliary agent and a stabilizing agent, wherein the alumina-containing raw material comprises alumina and aluminum hydroxide, and the use amount of the aluminum hydroxide is 5-10% of the total mass of the alumina-containing raw material; the dosage of the sodium removing agent is 0.1% -1% of the total mass of the alumina-containing raw material; the consumption of the induced phase change growth auxiliary agent is 0.5-2% of the total mass of the alumina-containing raw material; the dosage of the stabilizer is 0.05 to 0.1 percent of the total mass of the alumina-containing raw material.
Preferably, the dosage of the sodium removing agent is 0.5-1% of the total mass of the alumina-containing raw material; the consumption of the induced phase change growth auxiliary agent is 1% -2% of the total mass of the alumina-containing raw material; the amount of the stabilizer is 0.1% of the total mass of the alumina-containing raw material.
Further preferably, the dosage of the sodium removing agent is 0.6 to 0.8 percent of the total mass of the alumina-containing raw material; the consumption of the induced phase change growth auxiliary agent is 1.2-1.6% of the total mass of the alumina-containing raw material.
Preferably, the sodium removing agent is at least one selected from aluminum chloride, ammonium chloride and boric acid, and the purity is more than or equal to 99%.
Preferably, the phase-change-inducing growth promoter is at least one selected from calcium chloride, barium chloride and boron oxide.
Preferably, the stabilizer is at least one selected from cerium oxide and lanthanum oxide, and the purity is more than or equal to 99%.
Preferably, the median particle diameter D50 of the monocrystalline spherical alpha alumina is more than or equal to 25 mu m.
The second aspect of the invention provides a preparation method of the large single crystal spheroid alpha alumina, which specifically comprises the following steps:
(1) Adding an alumina-containing raw material, a sodium removing agent, an induced phase change growth auxiliary agent and a stabilizing agent into a mixer according to a proportion, and uniformly mixing to obtain a mixture;
(2) Placing the mixed mixture into kiln furniture, placing the kiln furniture into a high-temperature kiln, and sintering according to a three-stage heating and heat-preserving strategy to obtain a sintered product;
(3) And sequentially carrying out disintegration, washing and drying on the sintering product to obtain the large monocrystal spherical alpha alumina.
Preferably, the mixer in the step (1) is a V-shaped mixer, and the mixing time is 0.5-2 h.
Preferably, the three-stage temperature rise and heat preservation strategy in the step (2) is specifically as follows: the first section: heating to 600-800 ℃, and preserving heat for 2-4 h; and a second section: heating to 1200-1350 ℃, and preserving heat for 2-6 h; third section: heating to 1450-1550 ℃, and preserving heat for 4-10 h; the incomplete reaction can be caused by too low temperature or too short heat preservation time, the general reaction effect is positively correlated with the temperature and the heat preservation time, the temperature is increased to a certain condition, the granularity and the morphology index are not obviously optimized any more, and only the gas consumption is increased.
Further preferably, the three-stage temperature rise and heat preservation strategy in the step (2) is specifically as follows: the first section: heating to 650-750 ℃, and preserving heat for 2-4 h; and a second section: heating to 1250-1300 ℃, and preserving heat for 2-4 h; third section: heating to 1450-1500 ℃, and preserving heat for 4-8 h.
Preferably, the temperature rise rate of the first stage is 2 to 10 ℃/min, more preferably 2 to 5 ℃/min; the temperature rising rate of the second section is 2-5 ℃/min; the temperature rising rate of the third stage is 0.5-2 ℃/min, and more preferably 0.5-1.5 ℃/min; each auxiliary agent has gasification reaction in the process of heating to the heat preservation section, and if the heating rate is too slow, more atmosphere is dissipated, and the reaction concentration is reduced; if the temperature rising rate is too high, the temperature is uneven, the local temperature is too high, so that partial auxiliary agent is decomposed and invalid, the atmosphere pressure is rapidly increased and dissipated, and the reaction effect is poor.
Preferably, kiln furniture used in the step (2) is made of corundum, and is sealed by a cover made of the same material.
Preferably, the high temperature kiln is a shuttle kiln or a tunnel kiln.
Preferably, in the step (3), the washing is performed after the washing by pure water, wherein the acid used for the washing is selected from one of sulfuric acid, hydrochloric acid and nitric acid, and the conductivity of the pure water used for the washing is less than or equal to 5 mu s/cm.
Preferably, the washing step is specifically: adding purified water into the disintegrated material to adjust the solid content to 20-30%, adding acid to adjust the pH of slurry to 1, fully stirring for 2-6 h, naturally precipitating, discharging acid liquor, and washing with purified water to neutrality.
Compared with the prior art, the invention has the following beneficial effects:
the median particle diameter D50 of the large monocrystalline spherical alpha alumina is more than or equal to 25 mu m, and the specific surface area is less than or equal to 0.07m 2 The oil absorption value is low, and the defects of the existing spherical or spheroidal alumina are overcome; the alpha alumina has normal particle size distribution, extremely narrow particle size distribution, can be used for preparing high heat conduction products independently, can be used as an additive component for reasonably compounding with other heat conduction fillers, has good dispersibility and wettability in an epoxy resin and silicone rubber system, has high addition part and excellent comprehensive performance, and can be used for preparing high heat conduction productsAs a high-quality filler for preparing high-heat-conductivity interface materials;
in the existing two-stage sintering process, after the first-stage sintering, the sintering product is generally a worm-shaped aggregate, the further growth of crystals is influenced, the part with a more regular shape is sintered again by crushing and screening to remove the part with incomplete crystal growth, the growth defect is modified to realize the purpose of spheroidizing, the process is complicated, the original crystal grains are damaged in the process of disintegration, and the surface of the final product is not smooth; according to the invention, through setting reasonable temperature rise and heat preservation time, a large amount of gas phase is generated in the middle and low temperature sections by adding aluminum hydroxide and a low melting point mineralizer, the compactness of materials is reduced, the generation of vermicular shape is reduced, and conditions are created for the crystal production and spheroidization in the high temperature section; the intermediate sintering process does not need to take out and modify, so that the process flow is simplified, the production cost is reduced, and the industrialization is easy to realize;
the preparation process adopts a gradual heating strategy, and the highest temperature is controlled at 1550 ℃, so that the effects of energy conservation and environmental protection are achieved, and the equipment loss is reduced;
the invention selects the fluorine-free, safe, cheap and easily available composite sintering auxiliary agent, and each auxiliary agent plays a good synergistic effect in a reasonable proportion range, is clean and environment-friendly, avoids the corrosion of volatile components to equipment and kiln furniture, avoids environmental pollution and prolongs the service life of the equipment.
[ description of the drawings ]
FIG. 1 is a Scanning Electron Microscope (SEM) image of a sample prepared according to example 3 of the present invention;
FIG. 2 is a particle size distribution diagram of a sample prepared in example 3 of the present invention.
[ detailed description ] of the invention
The invention is illustrated by the following specific examples, but is in no way limited thereto, in order to make the objects, technical solutions and advantages of the invention more apparent. The following description of the preferred embodiments of the invention is merely illustrative of the invention and should not be taken as limiting the invention, it being understood that any modifications, equivalents, and improvements made within the spirit and principles of the invention are intended to be included within the scope of the invention.
In the following examples, the technical alumina meets the various brands of GB/T24487-2022 alumina standards, and AO-1 and AO-G brands are preferred.
The aluminum hydroxide requires a moisture content of < 0.2%, na 2 O is less than 0.4%; the function of the catalyst is that the catalyst releases vapor and contracts and refines in the sintering dehydration process, and the catalyst is attached to the surface of alumina, so that the material porosity is increased, and the catalyst is beneficial to the gas phase mass transfer process after the mineralizer is gasified.
Example 1
D50=89 μm industrial alumina 950g, aluminum hydroxide 50g, aluminum chloride 1g, boron oxide 5g and lanthanum oxide 0.5g are mixed for 0.5h in a V-shaped mixer, and the mixture is uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 600 ℃ at a heating rate of 2 ℃/min, and preserving the heat for 2 hours; then continuously heating to 1200 ℃ at the heating rate of 2 ℃/min, preserving heat for 2 hours, continuously heating to 1450 ℃ at the heating rate of 2 ℃/min, and preserving heat for 4 hours to obtain a sintered product;
the sintered product was disintegrated, washed and dried to give a single crystal spheroidal alpha alumina having d50=26.6 μm.
Example 2
D50 = 89 μm industrial alumina 900g, aluminum hydroxide 100g, boric acid 2g, barium chloride 10g and lanthanum oxide 0.5g are mixed in a V-shaped mixer for 1h and uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 650 ℃ at a heating rate of 4 ℃/min, and preserving the heat for 2 hours; continuously heating to 1250 ℃ at a heating rate of 2 ℃/min, preserving heat for 2h, then continuously heating to 1450 ℃ at a heating rate of 1 ℃/min, and preserving heat for 5h to obtain a sintered product;
the sintered product was disintegrated, washed and dried to give a single crystal spheroidal alpha alumina having d50=27.7 μm.
Example 3
D50 = 89 μm industrial alumina 900g, aluminum hydroxide 100g, ammonium chloride 2g, calcium chloride 5g, cerium oxide 0.5g are mixed in a V-shaped mixer for 1h, and the mixture is uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 600 ℃ at a heating rate of 5 ℃/min, and preserving the temperature for 3 hours; continuously heating to 1250 ℃ at a heating rate of 3 ℃/min, preserving heat for 3 hours, then continuously heating to 1450 ℃ at a heating rate of 0.5 ℃/min, and preserving heat for 4 hours to obtain a sintered product;
the sintered product was disintegrated, washed and dried to give a single crystal spheroidal alpha alumina having d50=31.1 μm.
Example 4
D50 = 89 μm industrial alumina 900g, aluminum hydroxide 100g, ammonium chloride 5g, calcium chloride 10g and cerium oxide 1g are mixed in a V-shaped mixer for 1h and uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 750 ℃ at a heating rate of 5 ℃/min, and preserving the heat for 2 hours; continuously heating to 1300 ℃ at a heating rate of 5 ℃/min, preserving heat for 3 hours, then continuously heating to 1500 ℃ at a heating rate of 1.5 ℃/min, and preserving heat for 6 hours to obtain a sintered product;
the sintered product was disintegrated, washed and dried to give a single crystal spheroidal alpha alumina having d50=35.9 μm.
Example 5
D50 = 89 μm industrial alumina 900g, aluminum hydroxide 100g, aluminum chloride 6g, barium chloride 12g and cerium oxide 1g are mixed for 2 hours in a V-shaped mixer, and the mixture is uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 750 ℃ at a heating rate of 5 ℃/min, and preserving the heat for 2 hours; continuously heating to 1300 ℃ at a heating rate of 5 ℃/min, preserving heat for 3 hours, then continuously heating to 1500 ℃ at a heating rate of 1.5 ℃/min, and preserving heat for 6 hours to obtain a sintered product;
the sintered product was disintegrated, washed and dried to give a single crystal spheroidal alpha alumina having d50=45.8 μm.
Example 6
D50 = 89 mu m industrial alumina 900g, aluminum hydroxide 100g, aluminum chloride 8g, boron oxide 16g and lanthanum oxide 1g are mixed in a V-shaped mixer for 2 hours and uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 750 ℃ at a heating rate of 5 ℃/min, and preserving the temperature for 4 hours; continuously heating to 1350 ℃ at a heating rate of 2 ℃/min, preserving heat for 4 hours, then continuously heating to 1550 ℃ at a heating rate of 0.5 ℃/min, and preserving heat for 8 hours to obtain a sintered product;
the sintered product was disintegrated, washed and dried to give a single crystal spheroidal alpha alumina having d50=45.4 μm.
Example 7
D50 = 89 mu m industrial alumina 900g, aluminum hydroxide 100g, aluminum chloride 10g, boron oxide 20g and lanthanum oxide 1g are mixed in a V-shaped mixer for 2 hours and uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 750 ℃ at a heating rate of 5 ℃/min, and preserving the temperature for 4 hours; continuously heating to 1350 ℃ at a heating rate of 2 ℃/min, preserving heat for 4 hours, then continuously heating to 1550 ℃ at a heating rate of 0.5 ℃/min, and preserving heat for 8 hours to obtain a sintered product;
the sintered product was disintegrated, washed and dried to give a single crystal spheroidal alpha alumina having d50=42.9 μm.
Example 8
The difference from example 5 is that the temperature rising rate of the first stage is 10 ℃/min, the temperature rising rate of the second stage is 5 ℃/min, and the temperature rising temperature of the third stage is 2 ℃/min;
the single crystal, spheroidal alpha alumina finally produced, has d50=36.7 μm. Compared with the example 5, the particle size of the prepared alpha alumina is obviously smaller, probably because the temperature rising rate is too high, so that the temperature is uneven, and the local temperature is too high, so that part of the auxiliary agent is decomposed and fails.
Example 9
The difference from example 5 is that the temperature rising rate of the first stage is 2 ℃/min, the temperature rising rate of the second stage is 2 ℃/min, and the temperature rising temperature of the third stage is 0.5 ℃/min;
the single crystal, spheroidal alpha alumina finally produced, has d50=28.3 μm. The particle size of the produced alpha alumina is significantly smaller than that of example 5, probably because the rate of temperature rise is too slow, so that the atmosphere is more dissipated, resulting in a decrease in the reaction concentration.
Example 10
The difference from example 5 is that the first stage has a soak temperature of 800℃and a soak time of 4 hours, the second stage has a soak temperature of 1350℃and a soak time of 6 hours, and the third stage has a soak temperature of 1550℃and a soak time of 10 hours.
The single crystal, spheroidal alpha alumina finally prepared, had d50=45.9 μm. Compared with example 5, the particle size of the prepared alpha alumina is not improved obviously, which shows that the alpha alumina has basically completely reacted at the heat preservation temperature and the heat preservation time defined in example 5, and therefore, no great breakthrough is caused by continuously increasing the heat preservation time.
Example 11
The difference from example 5 is that the first stage has a holding temperature of 600℃and a holding time of 2h, the second stage has a holding temperature of 1200℃and a holding time of 2h, and the third stage has a holding temperature of 1450℃and a holding time of 4h.
The single crystal, spheroidal alpha alumina finally prepared, had d50=26.9 μm. The particle size of the alpha alumina produced was significantly smaller than in example 5, possibly with insufficient holding temperature and holding time, so that no reaction was complete.
Comparative example 1
The difference from example 1 is that no aluminum hydroxide was added; the method comprises the following steps:
mixing 1000g of D50=89 mu m industrial alumina, 2.5g of aluminum chloride, 5g of boron oxide and 0.5g of lanthanum oxide for 0.5h in a V-shaped mixer, and uniformly mixing;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 600 ℃ at a heating rate of 2 ℃/min, and preserving the heat for 2 hours; then continuously heating to 1200 ℃ at the heating rate of 2 ℃/min, preserving heat for 2 hours, continuously heating to 1450 ℃ at the heating rate of 2 ℃/min, and preserving heat for 4 hours to obtain a sintered product;
the sintered product was disintegrated, washed and dried to give a single crystal spheroidal alpha alumina having d50=22.4 μm.
Comparative example 2
The difference from example 1 is that the amounts of the auxiliaries are different, in particular as follows:
d50=89 μm industrial alumina 950g, aluminum hydroxide 50g, aluminum chloride 10g, boron oxide 25g and lanthanum oxide 1g are mixed for 0.5h in a V-shaped mixer and uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 600 ℃ at a heating rate of 2 ℃/min, and preserving the heat for 2 hours; then continuously heating to 1200 ℃ at the heating rate of 2 ℃/min, preserving heat for 2 hours, continuously heating to 1450 ℃ at the heating rate of 2 ℃/min, and preserving heat for 4 hours to obtain a sintered product;
the sintered product was disintegrated, washed and dried to obtain a single crystal spheroidic alpha alumina, the d50=31.0 μm, although the particle size was increased compared with example 1, the prepared product had a large amount of auxiliary agent residue, slightly lower test purity, and had a certain influence on the morphology, the microscopic morphology of the product was poor, and the specific surface area was large.
Comparative example 3
The difference from example 1 is that the kinds of the auxiliary agents are different, specifically as follows:
d50=89 μm industrial alumina 950g, aluminum hydroxide 50g, aluminum nitrate 1g, boron oxide 5g and lanthanum oxide 0.5g are mixed for 0.5h in a V-shaped mixer, and the mixture is uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 600 ℃ at a heating rate of 2 ℃/min, and preserving the heat for 2 hours; then continuously heating to 1200 ℃ at the heating rate of 2 ℃/min, preserving heat for 2 hours, continuously heating to 1450 ℃ at the heating rate of 2 ℃/min, and preserving heat for 4 hours to obtain a sintered product;
the sintered product is disintegrated, washed and dried to obtain single crystal spherical alpha alumina with d50=23.7 microns, which is probably because aluminum nitrate is easy to decompose at high temperature and cannot effectively play the role.
Comparative example 4
The difference with example 1 is that the first stage heat preservation temperature is 500 ℃ and the heat preservation time is 5 hours; the finally prepared alpha alumina has d50=20.4 μm, the particle size distribution is widened, and the uniformity of the particle morphology is deteriorated.
Comparative example 5
The difference with example 1 is that the first stage heat preservation temperature is 900 ℃ and the heat preservation time is 2h; the finally produced alpha alumina, d50=24.1 μm, had a broad particle size distribution.
Comparative example 6
The difference with example 1 is that the second stage heat preservation temperature is 1100 ℃ and the heat preservation time is 7h; finally, the obtained alpha alumina has d50=23.3 μm, the particle size distribution is widened, and the alpha conversion rate is reduced.
Comparative example 7
The difference with example 1 is that the second stage heat preservation temperature is 1400 ℃ and the heat preservation time is 2h; finally produced is alpha alumina, d50=25.8 μm, the particle size distribution is widened, and the alpha conversion is reduced.
Comparative example 8
The difference with the embodiment 1 is that the third section has a heat preservation temperature of 1300 ℃ and a heat preservation time of 12 hours; finally produced alpha alumina, d50=21.7 μm, broadened in particle size distribution and lowered in alpha conversion.
Comparative example 9
The difference with the embodiment 1 is that the temperature of the third section is 1600 ℃ and the heat preservation time is 3h; finally prepared is alpha alumina, d50=26.2 μm.
Comparative example 10
The difference from example 1 is that the temperature rising rate of the first stage is 1 ℃/min; the finally prepared alpha alumina, d50=20.1 μm, had poor morphology.
Comparative example 11
The difference from example 1 is that the temperature rising rate of the first stage is 12 ℃/min; the finally prepared alpha alumina has d50=24.6 μm, uneven particle morphology and fine flaky crystal generation.
Comparative example 12
The difference from example 1 is that the temperature rising rate of the second stage is 1 ℃/min; finally prepared is alpha alumina, d50=26.5 μm.
Comparative example 13
The difference from example 1 is that the temperature rising rate of the second stage is 8 ℃/min; the finally prepared alpha alumina has d50=23.1 μm, slightly bad morphology and reduced alpha conversion rate.
Comparative example 14
The difference from example 1 is that the temperature rising rate in the third stage is 0.2 ℃/min; the finally produced alpha alumina, d50=24.8 μm, had a reduced alpha conversion.
Comparative example 15
The difference from example 1 is that the temperature rising rate in the third stage is 4 ℃/min; the finally produced alpha alumina, d50=23.6 μm, had a reduced alpha conversion.
Comparative example 16
The difference with the embodiment 1 is that a section of temperature rise and heat preservation strategy is adopted, and the specific steps are as follows:
d50=89 μm industrial alumina 950g, aluminum hydroxide 50g, aluminum chloride 2.5g, boron oxide 5g and lanthanum oxide 0.5g are mixed for 0.5h in a V-shaped mixer, and the mixture is uniformly mixed;
the mixture is put into kiln furniture, sealed by a sealing cover and placed into a kiln for calcination;
raising the temperature to 1550 ℃ at a heating rate of 2 ℃/min, and preserving the temperature for 4 hours to obtain a sintered product;
the sintered product is disintegrated, washed and dried to obtain the monocrystal spherical alpha alumina with d50=18.6 microns, poor appearance, wide granularity distribution and low conversion rate.
The samples prepared in the above examples and comparative examples were tested for comprehensive indexes such as particle size, oil absorption value, conductivity, specific surface area, alpha conversion rate, etc., and the results are shown in the following table;
table 1 results of the various index tests
As can be seen from the table, the graph 1 and the graph 2, the alpha alumina prepared by the method has a large monocrystal sphere-like shape, wherein the median particle size is larger than 25 μm, the particle size is in normal distribution, the particle size distribution is extremely narrow, in addition, the alpha conversion rate is higher than 99.5%, the specific surface area is small, the oil absorption value is low, and the defects of the indexes of the existing spherical or sphere-like alumina in all aspects are overcome.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that it will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the principles of the invention, which is also intended to be regarded as the scope of the invention.
Claims (10)
1. The large single crystal spherical alpha alumina is characterized by being formed by calcining an alumina-containing raw material, a sodium removing agent, an induced phase change growth auxiliary agent and a stabilizing agent, wherein the alumina-containing raw material comprises alumina and aluminum hydroxide, and the use amount of the aluminum hydroxide is 5% -10% of the total mass of the alumina-containing raw material; the dosage of the sodium removing agent is 0.1% -1% of the total mass of the alumina-containing raw material; the consumption of the induced phase change growth auxiliary agent is 0.5-2% of the total mass of the alumina-containing raw material; the dosage of the stabilizer is 0.05 to 0.1 percent of the total mass of the alumina-containing raw material.
2. The large single-crystal spherical alpha alumina according to claim 1, wherein the amount of the sodium removing agent in the large single-crystal spherical alpha alumina is 0.5% -1% of the total mass of the alumina-containing raw material; the consumption of the induced phase change growth auxiliary agent is 1% -2% of the total mass of the alumina-containing raw material; the amount of the stabilizer is 0.1% of the total mass of the alumina-containing raw material.
3. The large single crystal spheroidal alpha alumina according to claim 1, wherein the sodium removing agent is selected from at least one of aluminum chloride, ammonium chloride, boric acid.
4. The large single crystal spheroidal alpha alumina according to claim 1, wherein the phase change inducing growth promoter is selected from at least one of calcium chloride, barium chloride, boron oxide.
5. The large single crystal spheroidal alpha alumina according to claim 1, wherein the stabilizer is selected from at least one of cerium oxide, lanthanum oxide.
6. The method for producing a large single crystal spheroidal alpha alumina according to any one of claims 1 to 5, comprising the steps of:
(1) Adding an alumina-containing raw material, a sodium removing agent, an induced phase change growth auxiliary agent and a stabilizing agent into a mixer according to a proportion, and uniformly mixing to obtain a mixture;
(2) Placing the mixed mixture into kiln furniture, placing the kiln furniture into a high-temperature kiln, and sintering according to a three-stage heating and heat-preserving strategy to obtain a sintered product;
(3) And sequentially carrying out disintegration, washing and drying on the sintered product to obtain the large monocrystal spherical alpha alumina.
7. The method for preparing large single crystal spherical alpha alumina according to claim 6, wherein the three-stage temperature rise and preservation strategy in the step (2) is specifically as follows: the first section: heating to 600-800 ℃, and preserving heat for 2-4 h; and a second section: heating to 1200-1350 ℃, and preserving heat for 2-6 h; third section: heating to 1450-1550 ℃, and preserving heat for 4-10 h.
8. The method for producing a large single crystal spheroidal alpha alumina according to claim 7, wherein the temperature rising rate of the first stage is 2 to 10 ℃/min; the temperature rising rate of the second section is 2-5 ℃/min; the temperature rising rate of the third section is 0.5-2 ℃/min.
9. The method for producing large single crystal spheroidal alpha alumina according to claim 6, wherein kiln furniture used in step (2) is corundum material, and is sealed with a cover of the same material; the high-temperature kiln is a shuttle kiln or a tunnel kiln.
10. The method for producing large single crystal spherical alpha alumina according to claim 6, wherein the washing in the step (3) is washing with pure water after washing with acid, wherein the acid used for the washing is one selected from sulfuric acid, hydrochloric acid and nitric acid, and the pure water used for the washing has a conductivity of 5 μs/cm or less.
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|---|---|---|---|---|
| DE1767511A1 (en) * | 1967-05-19 | 1971-09-09 | Giulini Gmbh Geb | Process for the production of low sodium oxide alumina |
| US4374119A (en) * | 1980-09-23 | 1983-02-15 | Swiss Aluminium Ltd. | Process for the production of coarse crystalline alumina |
| JPH05294613A (en) * | 1991-11-28 | 1993-11-09 | Showa Denko Kk | Spherical corundum particle |
| US5340781A (en) * | 1986-07-14 | 1994-08-23 | Showa Denko Kabushiki Kaisha | Spherical corundum particles, process for preparation thereof and rubber or plastic composition having high thermal conductivity and having spherical corundum paticles incorporated therein |
| CN113184886A (en) * | 2021-04-14 | 2021-07-30 | 雅安百图高新材料股份有限公司 | Preparation method and product of high-thermal-conductivity spherical alumina |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1767511A1 (en) * | 1967-05-19 | 1971-09-09 | Giulini Gmbh Geb | Process for the production of low sodium oxide alumina |
| US4374119A (en) * | 1980-09-23 | 1983-02-15 | Swiss Aluminium Ltd. | Process for the production of coarse crystalline alumina |
| US5340781A (en) * | 1986-07-14 | 1994-08-23 | Showa Denko Kabushiki Kaisha | Spherical corundum particles, process for preparation thereof and rubber or plastic composition having high thermal conductivity and having spherical corundum paticles incorporated therein |
| JPH05294613A (en) * | 1991-11-28 | 1993-11-09 | Showa Denko Kk | Spherical corundum particle |
| CN113184886A (en) * | 2021-04-14 | 2021-07-30 | 雅安百图高新材料股份有限公司 | Preparation method and product of high-thermal-conductivity spherical alumina |
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