CN114057212A - Preparation method of high-specific surface superfine alumina powder and coating material - Google Patents
Preparation method of high-specific surface superfine alumina powder and coating material Download PDFInfo
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- CN114057212A CN114057212A CN202111404458.XA CN202111404458A CN114057212A CN 114057212 A CN114057212 A CN 114057212A CN 202111404458 A CN202111404458 A CN 202111404458A CN 114057212 A CN114057212 A CN 114057212A
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims abstract description 122
- 239000000463 material Substances 0.000 title claims abstract description 30
- 239000000843 powder Substances 0.000 title claims abstract description 30
- 239000011248 coating agent Substances 0.000 title claims abstract description 22
- 238000000576 coating method Methods 0.000 title claims abstract description 22
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 claims abstract description 35
- 230000000694 effects Effects 0.000 claims abstract description 27
- 238000001354 calcination Methods 0.000 claims abstract description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000013078 crystal Substances 0.000 claims description 39
- 229910001593 boehmite Inorganic materials 0.000 claims description 38
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 38
- 239000002245 particle Substances 0.000 claims description 28
- 238000006243 chemical reaction Methods 0.000 claims description 24
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 20
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 11
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 10
- 229910052744 lithium Inorganic materials 0.000 claims description 10
- 238000003837 high-temperature calcination Methods 0.000 claims description 9
- 239000000126 substance Substances 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 238000005253 cladding Methods 0.000 claims 1
- 238000011068 loading method Methods 0.000 claims 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 abstract description 11
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 238000005245 sintering Methods 0.000 abstract description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract 2
- 239000002912 waste gas Substances 0.000 abstract 2
- 239000003795 chemical substances by application Substances 0.000 abstract 1
- 239000012071 phase Substances 0.000 abstract 1
- 239000007790 solid phase Substances 0.000 abstract 1
- 238000001179 sorption measurement Methods 0.000 abstract 1
- 239000010405 anode material Substances 0.000 description 15
- 239000010406 cathode material Substances 0.000 description 15
- 238000002441 X-ray diffraction Methods 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- 208000020401 Depressive disease Diseases 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 238000000635 electron micrograph Methods 0.000 description 3
- 239000004088 foaming agent Substances 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 229920002521 macromolecule Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 1
- 229920001213 Polysorbate 20 Polymers 0.000 description 1
- NWGKJDSIEKMTRX-AAZCQSIUSA-N Sorbitan monooleate Chemical compound CCCCCCCC\C=C/CCCCCCCC(=O)OC[C@@H](O)[C@H]1OC[C@H](O)[C@H]1O NWGKJDSIEKMTRX-AAZCQSIUSA-N 0.000 description 1
- LWZFANDGMFTDAV-BURFUSLBSA-N [(2r)-2-[(2r,3r,4s)-3,4-dihydroxyoxolan-2-yl]-2-hydroxyethyl] dodecanoate Chemical compound CCCCCCCCCCCC(=O)OC[C@@H](O)[C@H]1OC[C@H](O)[C@H]1O LWZFANDGMFTDAV-BURFUSLBSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- SWLVFNYSXGMGBS-UHFFFAOYSA-N ammonium bromide Chemical compound [NH4+].[Br-] SWLVFNYSXGMGBS-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- WOWHHFRSBJGXCM-UHFFFAOYSA-M cetyltrimethylammonium chloride Chemical compound [Cl-].CCCCCCCCCCCCCCCC[N+](C)(C)C WOWHHFRSBJGXCM-UHFFFAOYSA-M 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000002001 electrolyte material Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 235000010486 polyoxyethylene sorbitan monolaurate Nutrition 0.000 description 1
- 235000010482 polyoxyethylene sorbitan monooleate Nutrition 0.000 description 1
- 229920000053 polysorbate 80 Polymers 0.000 description 1
- -1 polytetrafluoroethylene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 235000011067 sorbitan monolaureate Nutrition 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- GPRLSGONYQIRFK-MNYXATJNSA-N triton Chemical compound [3H+] GPRLSGONYQIRFK-MNYXATJNSA-N 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention relates to the technical field of preparation of aluminum oxide, and discloses a preparation method of high-specific-surface-area ultrafine aluminum oxide powder. The preparation method of the high-specific surface area superfine alumina powder has the advantages that the preparation method is simple in process, and the obtained high-specific surface area superfine alumina has good coating performance and stronger binding force with other materials. The material has high activity, and a mixed phase structure is formed after solid-phase calcination, so that the material not only keeps good activity, but also has good stability. In addition, no sintering aid or pore-forming agent is added in the calcining process, so that the alumina with high specific surface area can be prepared easily. And the waste gas is water vapor, can reach the national waste gas emission standard only by activated carbon adsorption, and has high environmental protection.
Description
Technical Field
The invention relates to the technical field of preparation of aluminum oxide, in particular to a preparation method of high-specific surface superfine aluminum oxide powder and a coating material.
Background
In recent years, the lithium battery industry is developed at a high speed, but the service life and the energy storage effect of the lithium battery are closely related to the electrolytic reaction efficiency of the ternary positive electrode material of the lithium battery. In the ternary anode material of the lithium ion battery, the anode material needs to react with lithium ions in electrolyte to realize discharge. However, other molecules in the electrolyte also react with the anode material, thereby reducing the service life of the anode material. Meanwhile, when the anode material is impacted by external force, the anode material is easy to explode, and danger is generated.
The applicant researches and discovers that the alpha-phase alumina has high resistivity, good insulating property, and good impact resistance and pressure resistance. The alpha-phase alumina is used as a coating material and coated on the ternary cathode material, and has a good protection effect. The process for preparing the aluminum oxide powder is produced by calcining and sintering aluminum hydroxide to generate a mixed heterogeneous phase structure with an alpha phase, a theta phase and a gamma phase. Wherein the gamma phase has an influence on the phase inversion process. Particularly, in the subsequent treatment process of the ternary cathode material of the lithium battery, the coating material needs to be treated at low temperature (1000 ℃) so that the gamma phase can not be completely converted into alpha-phase alumina with stable form. In addition, the prior art generally generates a powder structure with a smooth and defect-free surface, and the specific surface area (the specific surface area refers to the total surface area of the unit mass of the material) of the alumina powder is smaller. Because the specific surface area is relatively small, the material cannot be well combined with other substances.
In order to improve the bonding performance between the alumina powder and the ternary cathode material, the specific surface area of the alumina surface needs to be effectively increased.
In the technical scheme for preparing alumina powder in the prior art, the invention patent of publication No. CN103159243 discusses a method for preparing active alumina by hydrothermal method, deionized water is added under stirring, then monobasic acid, ammonium nitrate, hexadecyl trimethyl ammonium chloride or ammonium bromide, triton 100, span-80 or span-20, Tween-80 or-20 surfactant are added, and common aluminum-containing compound waste is placed in a high-pressure reaction kettle with a polytetrafluoroethylene lining; the common aluminum-containing compound waste is calculated by aluminum, and the molar ratio of the components is 50-100: 0.01-0.1: 0.01-3.5: 0.005-0.12: 1; heating the closed reaction kettle to 130-220 ℃, reacting at a constant temperature for 1-48 hours, stopping heating, cooling to below 90 ℃, discharging the materials, and washing the solid with deionized water for three times; drying the washed solid material at 120 ℃ until the analysis and detection are qualified; and (3) roasting in a muffle furnace, and ball-milling for 0-2 hours to obtain the activated alumina. The defects are as follows: the phase state of the prepared alumina is a mixed phase, which comprises an alpha phase, a theta phase and a gamma phase. The alpha phase has poor binding performance with the cathode material due to high stability, and cannot be used for a long time. And the surface of the generated alumina is free from defects, and the bonding performance with other materials is poor. The second defect is that: the large particle size of the alumina substance structure caused by the adoption of the acidic substance and the foaming agent causes the large gap size of the substance structure, so that various macromolecular substances in the electrolyte can enter the anode material for reaction, and the service life of the battery is shortened. Meanwhile, in the scheme, various acidic substances and foaming agents are required to be added, so that certain harm is caused to the environment.
The applicant further researches and discovers that a coating material needs to be introduced into a ternary cathode material of a lithium ion battery, and the coating material needs to have strong stability, impact resistance and proper particle size and gap between the particle sizes, and can be well combined with the cathode material into a whole, so that lithium ions in electrolyte can freely enter and exit the coating material to react with the cathode material, and other macromolecular substances in the electrolyte can be prevented from entering the coating material to react with the cathode material. Based on the applicant, the method for preparing the ultrafine alumina powder with the alpha phase and the theta two phases and the high specific surface by using boehmite as a raw material by a calcination process method is provided.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a preparation method of high specific surface area ultrafine alumina powder, which has the advantages of simple preparation, high environmental protection, high specific surface area, good coating performance and the like, and solves the problems of complex process and low coating performance.
(II) technical scheme
In order to achieve the purpose, the invention provides the following technical scheme:
a method for preparing high specific surface superfine alumina powder,
the method comprises the following steps: selecting seed crystal, and selecting 4kg of boehmite with the particle size of 10-30 as the seed crystal for later use;
step two: performing hydrothermal reaction, namely putting 1.6T of aluminum hydroxide and 4kg of 10-30nm seed crystal selected in the first step into a hydrothermal reaction kettle, and injecting 2.4T of pure water to obtain high-activity boehmite;
step three: high-temperature calcination, namely putting the high-activity boehmite obtained in the step two into a container for calcination, wherein the heating rate is 4-8 ℃/min, the final temperature is controlled at 1350 ℃, and the theta/alpha mixed phase alumina is obtained;
step four: airflow scattering, namely airflow scattering is carried out on the alumina of the theta/alpha mixed phase obtained in the third step to obtain alumina with the particle size of 0.3-2 mu m and the specific surface area of 18-50m2G dense and uniform porous mixed phase superfine alumina.
Preferably, the solid content of the raw materials added into the reaction kettle in the second step is 40%, and the filling amount is 80%.
Preferably, 0.4 to 3kg of 20nm boehmite seeds are added in step two.
Preferably, the temperature of the reaction kettle in the second step is 180 ℃, and the temperature is kept for 4H.
Preferably, 20nm of boehmite is selected in the first step.
Preferably, the device adopted by the airflow scattering is an airflow mill, and the pressure of the airflow mill is 0.4 Mpa.
Preferably, the calcining container in the third step is a sagger.
Preferably, the reaction kettle is a horizontal reaction kettle, a stirring paddle is not arranged in the reaction kettle, and reaction materials in the reaction kettle are driven to be fully mixed by rotating a reaction kettle container.
Preferably, the temperature of the container in the third step is controlled to 1350 ℃.
(III) advantageous effects
Compared with the prior art, the invention provides a preparation method of high specific surface superfine alumina powder, which has the following beneficial effects:
1. the preparation method of the high-specific surface superfine alumina powder comprises the step of firstly applying the alumina material with only alpha phase and theta phase to the coating material of the ternary cathode material of the lithium battery. In the low-temperature treatment process of the ternary cathode material of the lithium battery, the theta-phase alumina has good activity and good phase inversion performance, and is finally converted into a stable alpha-phase form. In the mixed phase forms of the alpha phase, the theta phase and the gamma phase in the prior art, the gamma phase can not be completely converted into the alpha phase at a low temperature (1000 ℃). Because the activity of the theta phase can be combined with the ternary cathode material into a whole in the phase inversion process, the alpha phase is completely generated after the phase inversion, and the alpha-phase alumina has good coating performance, the alumina prepared by the scheme can be tightly combined with the ternary cathode material, and the ternary cathode material can be coated by the alumina. By adding a small amount of the material, the good coating effect of the anode material can be realized, and simultaneously, the volume of the coating material is correspondingly small due to the small using amount of the coating material, so that the small occupation ratio of the anode material of the battery is realized.
2. Secondly, in the invention, after the aluminum oxide material is heated by gradually raising the temperature, the structural crystal lattice of boehmite can carry a crystal lattice water, and the crystal lattice water overflows from the crystal lattice at a certain temperature (380 ℃), so that pits where the crystal lattice is located are remained, and the surface of the aluminum oxide obtained after the treatment of the process steps of the invention forms a pit structure with the size of 30-150nm, thereby increasing the specific surface area of the aluminum oxide. In the invention, 10-30nm of boehmite is particularly selected as a seed crystal and the particle size of the finally prepared alumina powder is controlled by temperature to be 0.3-2 mu m. The particle size of 0.3-2 μm enables the gaps between the alumina material structures to allow nanometer-sized lithium ions to freely enter the anode material from the electrolyte from the gaps, and other large-sized electrolyte materials cannot enter the anode material from the gaps for reaction. Therefore, the electrolytic reaction is ensured, and the reduction of the service life and the influence of other substances without the reaction of the anode material on the anode material are prevented. Meanwhile, in the prior art, an acid-base solution and a foaming agent are adopted to perform surface depression treatment on sintered alumina to increase the specific surface area. However, the prepared alumina cannot be controlled to be a hetero-state of an alpha phase, a theta phase and a gamma phase, and the size of the prepared particle size cannot be controlled to produce a large-sized alumina material structure. The gaps among the large-size aluminum oxide are huge, so that not only can lithium ions freely shuttle, but also other macromolecular structures can freely shuttle into the coating material which reacts with the anode material to influence the service life of the lithium battery and is not suitable for being applied to the ternary anode material of the lithium battery, and meanwhile, the acid-base solution is adopted to pollute the environment.
3. Furthermore, the invention adopts high-activity boehmite which adopts 10-30nm seed crystal to induce the hydrothermal reaction of aluminum hydroxide and has a water molecular structure easy to dissipate. The overflow of water molecules in crystal lattices is controlled by selecting a specific temperature rise speed and heat preservation time so as to ensure that perforation or overlarge pore diameter cannot be caused, the generation of 30-150nm surface depression is obtained, and finally the alumina with a high specific surface is obtained.
The alumina powder with high specific surface area prepared by the invention is applied to the coating material of the ternary cathode material of the lithium battery, has the characteristics of high purity, small particle size, uniform distribution, large specific surface area, clean surface, no residual impurities, low apparent density, easy dispersion, stable crystalline phase, high hardness and good size stability, and can improve the performance of the ternary cathode material.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.
FIG. 1 is a schematic representation of a seed map in accordance with the present invention;
FIG. 2 is a schematic diagram of the spectrum of alumina prepared by the present invention;
FIG. 3 is an enlarged schematic view of FIG. 2;
FIG. 4 is a schematic representation of alumina that has not been treated by the process of the present invention;
FIG. 5 is a schematic structural view of boehmite according to the present invention;
FIG. 6 is a pure theta phase alumina XRD pattern;
FIG. 7 is an electron micrograph of 0.3 μm alumina;
FIG. 8 is an electron micrograph of 0.7 μm alumina;
FIG. 9 is an electron micrograph of alumina 2 μm;
FIG. 10 is a pure alpha phase alumina XRD pattern;
FIG. 11 is an alumina XRD pattern of the theta/alpha mixed phase.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows: a preparation method of high specific surface superfine alumina powder comprises the following steps:
the method comprises the following steps: selecting seed crystals, wherein 4kg of boehmite with the particle size of 20nm is selected as the seed crystals for later use;
step two: performing hydrothermal reaction, namely putting 1.6T of aluminum hydroxide and 4kg of 20nm seed crystal selected in the first step into a hydrothermal reaction kettle, and injecting 2.4T of pure water to obtain high-activity boehmite;
step three: high-temperature calcination, namely putting the high-activity boehmite obtained in the step two into a container for calcination, wherein the heating rate is 5 ℃/min, the final temperature is controlled at 1350 ℃, and the theta/alpha mixed phase alumina is obtained;
step four: airflow scattering, namely airflow scattering is carried out on the alumina of the theta/alpha mixed phase obtained in the third step to obtain alumina with the particle size of 0.3-2 mu m and the specific surface area of 18-50m2G dense and uniform porous mixed phase superfine alumina.
As shown in fig. 6, 10 and 11, the XRD patterns of pure theta phase alumina, pure alpha phase alumina and the XRD patterns of theta/alpha phase mixed phase alumina are shown, respectively. Wherein the theta phase alumina is formed at a calcination temperature below 1200 deg.C, the pure alpha phase alumina is formed at a temperature above 1500 deg.C, and the example uses a calcination temperature of 1350 deg.C. The XRD peaks in fig. 6 and 10 reflect corresponding phases, and a mixed state of the XRD pattern peaks in fig. 6 and the XRD pattern peaks in fig. 10 is clearly shown in fig. 11. A schematic representation of selected 20nm boehmite seeds in fig. 1, from which the size and structure of the seeds can be shown. After the process steps of the present invention, a map schematic diagram of the obtained high aspect ratio ultrafine alumina powder is shown in fig. 2, and fig. 3 is a partial enlarged view of fig. 2 for showing the dishing. It is clear from fig. 3 that recesses appear in the interior of the alumina structure, demonstrating that calcination produces a suitable recess structure, and that the dimensions range between 30nm and 150 nm. And a plurality of concave structures are uniformly distributed in the aluminum oxide coating, so that the specific surface area of the aluminum oxide is improved, and the coating performance is effectively improved. Fig. 4 corresponding to the graph is a schematic diagram of the alumina which is not processed by the technical scheme, and it can be clearly seen that the alumina structure is a compact structure.
And (4) conclusion: the alumina powder obtained by the treatment of the scheme of the embodiment has a multi-concave structure.
Example 2: a preparation method of high specific surface superfine alumina powder comprises the following steps: compared with the effect of reducing the mass of the seed crystal in the first embodiment
The method comprises the following steps: selecting seed crystals, wherein 4kg of boehmite with the particle size of 20nm is selected as the seed crystals for later use;
step two: performing hydrothermal reaction, namely putting 1.6T of aluminum hydroxide and 3kg of 20nm seed crystal selected in the first step into a hydrothermal reaction kettle, and injecting 2.4T of pure water to obtain high-activity boehmite;
step three: high-temperature calcination, namely putting the high-activity boehmite obtained in the step two into a container for calcination, wherein the heating rate is 5 ℃/min, the final temperature is controlled at 1350 ℃, and the theta/alpha mixed phase alumina is obtained;
step four:airflow scattering, namely airflow scattering is carried out on the alumina of the theta/alpha mixed phase obtained in the third step to obtain alumina with the particle size of 0.7 mu m and the specific surface area of 43m2G dense and uniform porous mixed phase superfine alumina.
Wherein FIG. 7 is a graph showing the particle size of boehmite obtained when the weight of the seed crystal was 4kg in example one, ranging from 232nm to 586.8 nm. The particle size of the alumina prepared in this example is clearly seen in the range of 226.1nm-1194nm in FIG. 8.
And (4) conclusion: it is shown that the reduction of the mass of the seed crystal can increase the particle size of the prepared alumina and reduce the specific surface area.
Comparative example 1
The preparation method of alumina is different from the first embodiment in that no boehmite seed crystal is added
The method comprises the following steps: performing hydrothermal reaction, namely putting 1.6T of aluminum hydroxide into a hydrothermal reaction kettle, and injecting 2.4T of pure water to obtain boehmite;
step two: high-temperature calcination, namely putting the high-activity boehmite obtained in the step two into a container for calcination, wherein the heating rate is 5 ℃/min, the final temperature is controlled at 1350 ℃, and alpha-phase alumina is obtained;
step three: airflow scattering, namely airflow scattering is carried out on the alpha-phase alumina obtained in the step three to obtain the alumina with the particle size of 2 mu m and the specific surface area of 5m2G dense and uniform porous pure alpha-phase superfine alumina. And the surface is free of significant dishing.
As can be seen from fig. 2, the prepared alumina structure has a porous structure.
And (4) conclusion: it is shown that in the process without adding the seed crystal, although the porous ultrafine alumina is obtained, the alumina finally obtained is pure alpha-phase ultrafine alumina.
Comparative example 2
Compared with the first embodiment, the preparation method of the alumina is characterized in that the final temperature is reduced to 1200 DEG C
The method comprises the following steps: selecting seed crystals, wherein 4kg of boehmite with the particle size of 20nm is selected as the seed crystals for later use;
step two: performing hydrothermal reaction, namely putting 1.6T of aluminum hydroxide and 4kg of 20nm seed crystal selected in the first step into a hydrothermal reaction kettle, and injecting 2.4T of pure water to obtain high-activity boehmite;
step three: high-temperature calcination, namely putting the high-activity boehmite obtained in the step two into a container for calcination, wherein the heating rate is 5 ℃/min, the final temperature is controlled at 1200 ℃, and theta-phase alumina is obtained;
step four: airflow scattering, namely airflow scattering is carried out on the theta-phase alumina obtained in the third step to obtain alumina with the particle size of 0.3 mu m and the specific surface area of 53m2Theta phase ultrafine alumina in a specific ratio of/g.
Fig. 6 shows a schematic diagram of the alumina pattern of the pure theta phase.
And (4) conclusion: indicating that the alumina prepared is pure theta phase at 1200 deg.c.
Comparative example 3
A method for preparing alumina, which is different from comparative example 2 in that the final temperature is controlled at 1500 ℃.
The method comprises the following steps: selecting seed crystals, wherein 4kg of boehmite with the particle size of 20nm is selected as the seed crystals for later use;
step two: performing hydrothermal reaction, namely putting 1.6T of aluminum hydroxide and 4kg of 20nm seed crystal selected in the first step into a hydrothermal reaction kettle, and injecting 2.4T of pure water to obtain high-activity boehmite;
step three: high-temperature calcination, namely putting the high-activity boehmite obtained in the step two into a container for calcination, wherein the heating rate is 5 ℃/min, the final temperature is controlled at 1500 ℃, and alpha-phase alumina is obtained;
step four: airflow scattering, namely airflow scattering is carried out on the alpha-phase alumina obtained in the step three to obtain the alumina with the particle size of 0.3 mu m and the specific surface area of 48m2Alpha phase ultrafine alumina in a/g ratio.
Fig. 10 is a diagram showing the alumina pattern of the pure alpha phase.
And (4) conclusion: indicating that the alumina prepared at 1500 c is a pure alpha phase.
Comparative example 4
Compared with the second comparative example, the preparation method of the alumina is characterized in that the temperature rise rate is controlled at 2 ℃/min
The method comprises the following steps: selecting seed crystals, wherein 4kg of boehmite with the particle size of 20nm is selected as the seed crystals for later use;
step two: performing hydrothermal reaction, namely putting 1.6T of aluminum hydroxide and 4kg of 20nm seed crystal selected in the first step into a hydrothermal reaction kettle, and injecting 2.4T of pure water to obtain high-activity boehmite;
step three: high-temperature calcination, namely putting the high-activity boehmite obtained in the step two into a container for calcination, wherein the heating rate is 2 ℃/min, the final temperature is controlled at 1200 ℃, and the alumina of the theta/alpha mixed phase is obtained;
step four: airflow scattering, namely airflow scattering is carried out on the theta/alpha mixed phase alumina obtained in the third step to obtain the alumina with the particle size of 0.3 mu m and the specific surface area of 6m2Theta/alpha mixed phase of ultrafine alumina in a/g ratio, but without significant surface dishing.
The surface of the alumina pattern shown in fig. 4 had no significant dishing.
And (4) conclusion: the alumina obtained by the technical proposal has the grain diameter of 0.3 μm and the specific surface area of 6m2The/g mixed phase superfine alumina has no obvious depressions on the surface, and the fact that the temperature rise rate can change the phase change in the alumina preparation process is obviously known, but too low temperature rise rate can cause the space after crystal lattice dehydration to be filled, so that the final alumina has no depressions on the surface.
Comparative example 5
Compared with the second embodiment, the preparation method of the alumina has the difference that the temperature rise rate is controlled at 10 ℃/min
The method comprises the following steps: selecting seed crystals, wherein 4kg of boehmite with the particle size of 20nm is selected as the seed crystals for later use;
step two: performing hydrothermal reaction, namely putting 1.6T of aluminum hydroxide and 4kg of 20nm seed crystal selected in the first step into a hydrothermal reaction kettle, and injecting 2.4T of pure water to obtain high-activity boehmite;
step three: high-temperature calcination, namely putting the high-activity boehmite obtained in the step two into a container for calcination, wherein the heating rate is 10 ℃/min, the final temperature is controlled at 1200 ℃, and the alumina of the theta/alpha mixed phase is obtained;
step four: airflow scattering, namely airflow scattering is carried out on the theta/alpha mixed phase alumina obtained in the third step to obtain the alumina with the particle size of 0.3 mu m and the specific surface area of 45m2The theta/alpha mixed phase of the ultrafine alumina is/g, but the surface has perforations or depressions with non-uniform pore diameters.
And (4) conclusion: although the mixed-phase ultrafine alumina having a particle size of 0.3 μm and a specific surface area of 45m2/g was obtained, it was found that the temperature increase rate was too high, and although surface depressions were generated, the lattice space on the surface of the alumina was too large after water loss or the alumina was directly perforated.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. A preparation method of high specific surface superfine alumina powder is characterized by comprising the following steps:
the method comprises the following steps: selecting seed crystal, wherein boehmite with the particle size of 10-30nm is selected as the seed crystal for later use;
step two: performing hydrothermal reaction, namely putting aluminum hydroxide and the 10-30nm seed crystal selected in the step one into a hydrothermal reaction kettle, and injecting pure water to obtain high-activity boehmite;
step three: high-temperature calcination, namely putting the high-activity boehmite obtained in the step two into a container for calcination, wherein the heating rate is 4-8 ℃/min, the final temperature is controlled at 1200-1500 ℃, and the alumina of the theta/alpha mixed phase is obtained;
step four: airflow scattering, namely airflow scattering is carried out on the alumina of the theta/alpha mixed phase obtained in the third step to obtain alumina with the particle size of 0.3-2 mu m and the specific surface area of 18-50m2G dense and uniform porous mixed phase superfine alumina.
2. The method for preparing the superfine alumina powder with high specific surface area as claimed in claim 1, wherein the content of the fixed substances in the raw materials added into the reaction kettle in the second step is 30-50%, and the volume loading of the reaction kettle is 70-90%.
3. The method for preparing high-aspect-ratio ultrafine alumina powder according to claim 1 or 2, wherein 0.4 to 3kg of boehmite seed crystals are added in the second step.
4. The method for preparing the ultrafine alumina powder with high specific surface area according to claim 1, wherein: the temperature of the reaction kettle in the second step is 160-200 ℃, and the temperature is kept for 3-5H.
5. The method for preparing high-surface-ratio ultrafine alumina powder according to claim 1, wherein 20nm boehmite is selected in the first step.
6. The method for preparing high-aspect-ratio ultrafine alumina powder according to claim 1, wherein the air flow scattering equipment is an air flow mill, and the pressure of the air flow mill is 0.3-0.5 Mpa.
7. The method of claim 1, wherein the calcining vessel in the third step is a sagger.
8. The method for preparing the ultrafine alumina powder with high specific surface area according to claim 1, wherein: the reaction kettle is a horizontal reaction kettle, a stirring paddle is not arranged in the reaction kettle, and reaction materials in the reaction kettle are driven to be fully mixed by rotating a reaction kettle container.
9. The method for preparing the ultrafine alumina powder with high specific surface area according to claim 1, wherein: the temperature of the container in the third step is controlled at 1350 ℃.
10. A cladding material applied to a lithium battery is characterized in that: the coating material is prepared from the alumina powder obtained by the method of claims 1-9.
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