CN113247930B - A kind of alpha-alumina and preparation method thereof - Google Patents
A kind of alpha-alumina and preparation method thereof Download PDFInfo
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- CN113247930B CN113247930B CN202110740014.7A CN202110740014A CN113247930B CN 113247930 B CN113247930 B CN 113247930B CN 202110740014 A CN202110740014 A CN 202110740014A CN 113247930 B CN113247930 B CN 113247930B
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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 428
- 238000002360 preparation method Methods 0.000 title claims abstract description 81
- 239000000843 powder Substances 0.000 claims abstract description 199
- 239000002243 precursor Substances 0.000 claims abstract description 137
- 238000005245 sintering Methods 0.000 claims abstract description 87
- 238000001816 cooling Methods 0.000 claims abstract description 54
- 238000000034 method Methods 0.000 claims abstract description 30
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 64
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 49
- 239000000203 mixture Substances 0.000 claims description 41
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 36
- 239000007788 liquid Substances 0.000 claims description 35
- 229910052757 nitrogen Inorganic materials 0.000 claims description 32
- 235000011089 carbon dioxide Nutrition 0.000 claims description 30
- 239000003153 chemical reaction reagent Substances 0.000 claims description 30
- 239000005457 ice water Substances 0.000 claims description 24
- 230000009467 reduction Effects 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 4
- 230000000717 retained effect Effects 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000011148 porous material Substances 0.000 abstract description 22
- 239000012535 impurity Substances 0.000 abstract description 9
- 230000008569 process Effects 0.000 abstract description 9
- 239000002245 particle Substances 0.000 abstract description 8
- 229910010272 inorganic material Inorganic materials 0.000 abstract description 2
- 239000011147 inorganic material Substances 0.000 abstract description 2
- 238000001035 drying Methods 0.000 description 48
- 239000000919 ceramic Substances 0.000 description 31
- 238000001914 filtration Methods 0.000 description 30
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 26
- 229910052782 aluminium Inorganic materials 0.000 description 25
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 25
- 239000000243 solution Substances 0.000 description 25
- 239000007787 solid Substances 0.000 description 24
- 230000008878 coupling Effects 0.000 description 23
- 238000010168 coupling process Methods 0.000 description 23
- 238000005859 coupling reaction Methods 0.000 description 23
- 238000010438 heat treatment Methods 0.000 description 23
- 230000001939 inductive effect Effects 0.000 description 23
- 125000005210 alkyl ammonium group Chemical group 0.000 description 22
- 239000000908 ammonium hydroxide Substances 0.000 description 22
- 238000006243 chemical reaction Methods 0.000 description 22
- 239000011888 foil Substances 0.000 description 22
- 238000010907 mechanical stirring Methods 0.000 description 22
- 238000012544 monitoring process Methods 0.000 description 22
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 22
- 238000003756 stirring Methods 0.000 description 21
- 230000000052 comparative effect Effects 0.000 description 16
- 229910052594 sapphire Inorganic materials 0.000 description 9
- 239000013078 crystal Substances 0.000 description 7
- 238000005507 spraying Methods 0.000 description 7
- 239000000463 material Substances 0.000 description 5
- 229910052593 corundum Inorganic materials 0.000 description 4
- -1 oxygen ions Chemical class 0.000 description 4
- 229910001845 yogo sapphire Inorganic materials 0.000 description 4
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical group [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 3
- 239000001569 carbon dioxide Substances 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 239000003507 refrigerant Substances 0.000 description 3
- SMZOGRDCAXLAAR-UHFFFAOYSA-N aluminium isopropoxide Chemical compound [Al+3].CC(C)[O-].CC(C)[O-].CC(C)[O-] SMZOGRDCAXLAAR-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000011946 reduction process Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 229910003158 γ-Al2O3 Inorganic materials 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- 229910021502 aluminium hydroxide Inorganic materials 0.000 description 1
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 229910001648 diaspore Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910001679 gibbsite Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 230000009972 noncorrosive effect Effects 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 229910001682 nordstrandite Inorganic materials 0.000 description 1
- 230000009965 odorless effect Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910001388 sodium aluminate Inorganic materials 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 229910006415 θ-Al2O3 Inorganic materials 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
- C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
- C01F7/442—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination in presence of a calcination additive
-
- 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
- C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- Compositions Of Oxide Ceramics (AREA)
Abstract
本申请提供一种α‑氧化铝及其制备方法，属于无机材料技术领域。α‑氧化铝的制备方法包括：氧化铝的前驱体完成烧结后，将经烧结得到的1000～1500℃的氧化铝粉体以5～200℃/s的降温速率降温至20℃以下。本申请采用快速冷却的方法能够还原部分氧化铝孔结构，氧化铝粉体在快速降温过程中，氧化铝部分粉体中的毛细管打开，孔结构的坍塌得到抑制，最终可还原部分微‑介孔结构，从而在一定程度上提高制得的α‑氧化铝的比表面积。整个制备流程简便，易操控，且不会引入新的杂质。制得的α‑氧化铝性能稳定，其比表面积在10m2/g以上，且粉体形貌较一致，颗粒分散性好，纯度较高。
The application provides an α-alumina and a preparation method thereof, belonging to the technical field of inorganic materials. The preparation method of α-alumina includes: after the alumina precursor is sintered, the 1000-1500°C alumina powder obtained by sintering is cooled to below 20°C at a cooling rate of 5-200°C/s. In the present application, the rapid cooling method can reduce part of the alumina pore structure. During the rapid cooling process of the alumina powder, the capillaries in the alumina part of the powder are opened, the collapse of the pore structure is suppressed, and finally part of the micro-mesopores can be reduced. structure, thereby increasing the specific surface area of the prepared α-alumina to a certain extent. The whole preparation process is simple and easy to control, and no new impurities are introduced. The prepared α-alumina has stable performance, its specific surface area is above 10 m 2 /g, the powder morphology is relatively consistent, the particle dispersibility is good, and the purity is high.
Description
Technical Field
The application relates to the technical field of inorganic materials, in particular to alpha-alumina and a preparation method thereof.
Background
The alpha-phase alumina powder belongs to a trigonal system, oxygen ions in the structure are approximately packed in a close-packed hexagonal way, and aluminum atoms are filled in octahedral gaps of the powder. alpha-Al2O3Generally, the aluminum hydroxide or other aluminum-containing compounds are used as raw materials and prepared by a high-temperature roasting process. The crystal form of the ceramic material is stable, the particle size distribution is uniform, the purity is high, the dispersion is high, the hardness is high, and the like, and the ceramic material can be widely applied to the fields of ceramics, electroceramics, refractory materials, high-grade insulating parts, high-purity refractory fibers, grinding materials for grinding and polishing, semiconductor materials and the like. alpha-Al after high-temperature sintering2O3The collapse of the pore structure is serious, the specific surface area is greatly reduced, and therefore, the alpha-Al2O3Powder materials are generally more inert. In the field of materials such as certain optics, catalysts and the like, the alpha-Al with higher specific surface area2O3The demand is large.
At present, the technology for improving the specific surface area of alumina mainly aims to improve methods such as synthesis of an alumina precursor and the like, so that the aim of preparing the alumina with high surface area is fulfilled. For example, organic aluminum salt and organic solvent are stirred and dissolved at a certain temperature, and after being uniformly mixed, an aqueous solution of organic alcohol is added to obtain an alumina precursor, and the alumina precursor with high specific surface area and porous structure is prepared by calcination. And mixing the sol-gel dispersion liquid with an inorganic aluminum salt solution to prepare a required alumina precursor, and calcining the blank to obtain the mesoporous alumina with high specific surface area.
The modification of alumina precursors by chemical methods is the most used method at present, and although these processes can better solve Al2O3The problem of lower specific surface area, but the synthesis process is more complex, the related parameters are difficult to control, and industrialization is difficult to realize. Meanwhile, some chemical reagents can bring in part of impurity elements, so that the purity of the alumina powder is reduced. Meanwhile, most of the prior art only aims at improving gamma-Al2O3The specific surface area of the catalyst is rarely increased in relation to the increase of alpha-Al2O3Technical method of specific surface area. In general, Al is in these different crystal forms2O3，α-Al2O3The specific surface area of (a) is minimal and difficult to control.
Disclosure of Invention
Provided are an alpha-alumina and a method for preparing the same, which can increase the specific surface area of the alpha-alumina.
The embodiment of the application is realized as follows:
in a first aspect, the present application provides a method for preparing alpha-alumina, comprising: and after the precursor of the alumina is sintered, cooling the 1000-1500 ℃ alumina powder obtained by sintering to below 20 ℃ at a cooling rate of 5-200 ℃/s.
In the technical scheme, the rapid cooling method is adopted, so that the pore structure of the alpha-alumina can be greatly improved, and the alpha-alumina powder with a large specific surface area is prepared.
With reference to the first aspect, in a first possible example of the first aspect of the present application, the alumina powder obtained by sintering is mixed with a reagent at 5 ℃ or lower within 1 to 30 seconds of completion of sintering of the precursor of alumina.
In the above example, the reagent of 5 ℃ or lower is uniformly mixed with the sintered alumina powder, so that the sintered alumina powder can be uniformly cooled to 20 ℃ or lower at a cooling rate of 5-200 ℃/s.
With reference to the first aspect, in a second possible example of the first aspect of the present application, a mass ratio of the alumina powder to the reagent is 1:50 to 500.
In the above example, when the mass ratio of the alumina powder to the reagent is 1: 50-500, the temperature of the sintered alumina powder can be uniformly reduced to below 20 ℃ at a cooling rate of 5-200 ℃/s.
In a third possible example of the first aspect of the present application in combination with the first aspect, the reagent includes any one or more of liquid nitrogen, dry ice, an ice-water mixture, and water having a temperature of 5 ℃.
In the above example, the liquid nitrogen and the dry ice are volatile at normal temperature, and no impurities remain in the prepared alpha-alumina powder; the ice-water mixture and the water with the temperature less than or equal to 5 ℃ can be volatilized by a drying method, and impurities can not be remained in the prepared alpha-alumina powder.
With reference to the first aspect, in a fourth possible example of the first aspect of the present application, the temperature of the liquid nitrogen is-200 to-140 ℃, and the temperature of the dry ice is-90 to-60 ℃.
With reference to the first aspect, in a fifth possible example of the first aspect of the present application, the reagent includes an ice water mixture and/or water with a temperature of less than or equal to 5 ℃, and after the alumina powder is cooled to below 20 ℃, the alumina powder is dried at 40 to 80 ℃ for 2 to 8 hours.
In the above example, the drying of the alumina powder at 40 to 80 ℃ for 2 to 8 hours can completely gasify the moisture in the alumina powder without affecting the pore structure of the produced α -alumina, i.e., without reducing the specific surface area of the produced α -alumina.
With reference to the first aspect, in a sixth possible example of the first aspect of the present application, before drying the alumina powder at 40 to 80 ℃ for 2 to 8 hours, the mixture of the alumina powder and the reagent is filtered, and the filter residue is retained.
In the above example, the mixture of alumina powder and water is filtered before drying, so that alumina powder with low water content can be obtained, and the filter residue is dried, thereby reducing the drying time.
With reference to the first aspect, in a seventh possible example of the first aspect of the present application, the temperature reduction rate of the alumina powder is monitored in real time by an inductively coupled thermometer.
In the above example, the temperature reduction rate of the alumina powder is monitored in real time by an inductively coupled thermometer, so that the temperature reduction rate of the alumina powder at 20 ℃ or higher is maintained at 5-200 ℃/s.
In an eighth possible example of the first aspect of the present application, in combination with the first aspect, the sintering temperature of the precursor of aluminum oxide is 1000 to 1500 ℃, and the sintering time is 1 to 8 hours.
In a second aspect, the present application provides an α -alumina, which is prepared according to the above-described α -alumina preparation method.
In the technical scheme, the alpha-alumina prepared by the method has higher specific surface area of 10m2More than g, consistent powder morphology, good particle dispersibility and higher purity.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is a scanning electron micrograph of α -alumina prepared in accordance with the present application.
Detailed Description
Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Alumina (Al)2O3) Is a common inorganic substance and can be widely applied to a plurality of fields. Known as Al2O3More than 8 crystal forms (rho, eta, gamma, chi, delta, theta, kappa and alpha-Al)2O3Etc.) according to O2-The arrangement structure can be Al2O3It is divided into two major classes of face-centered cubic structure and close-packed hexagonal structure. According to Al3+The sublattice can separate these two main classes into different phases, where γ -Al2O3Belonging to the cubic system, theta-Al2O3Is monoclinic system, alpha-Al2O3Is a trigonal system. gamma-Al2O3Transformation to a single theta crystal phase, theta-Al, at 900 deg.C2O3The transformation to alpha phase is slowly carried out at 1100 ℃, and the content of alpha phase is gradually increased along with the extension of the roasting time, and the alpha phase is completely transformed into stable alpha crystal phase at 1200 ℃. When the phases of the alumina such as gamma, theta and the like are transformed in the high-temperature roasting process, the pore structure can be completely collapsed, the specific surface area and the pore volume are sharply reduced, and finally, alpha-Al with a compact structure is formed2O3. When changing from theta phase to alpha phase, O2-Rearrangement occurs and structural reformation occurs, so the temperature required for phase transition is high, and the changes in specific surface area and pore size are significant in this process. alpha-Al2O3The specific surface area of the powder is small, namely, the powder capillary tube can shrink during high-temperature roasting to cause the collapse of a micro-mesoporous structure, namely, the collapse of the pore structure can generate hard agglomeration of powder particles, and the specific surface area is greatly reduced.
Existing improvements in alpha-Al2O3By improving the synthesis method of the alumina precursor, which often produces the alpha-Al2O3Impurities are introduced to reduce the prepared alpha-Al2O3The purity of the powder is complicated, and the industrialization is difficult to realize.
The following description will be made specifically for an α -alumina and a method for preparing the same in the examples of the present application:
the present application provides a method for preparing alpha-alumina, comprising: and after the precursor of the alumina is sintered, cooling the 1000-1500 ℃ alumina powder obtained by sintering to below 20 ℃ at a cooling rate of 5-200 ℃/s.
The inventor of the application finds that the alumina powder body after high-temperature sintering is in a high-temperature state, the collapsed pore structure on the surface of the powder body is still in a soft state temporarily, and the pore structure of the powder body is not shaped yet.
The adoption of a rapid cooling method can reduce part of the alumina pore structure: in the process of rapidly cooling the alumina powder, capillaries in the alumina part powder are opened, collapse of a pore structure is inhibited, and a part of micro-mesoporous structure can be reduced finally, so that the specific surface area of the prepared alpha-alumina is improved to a certain extent.
Optionally, the cooling rate of the alumina powder is 50-200 ℃/s.
Optionally, the cooling rate of the alumina powder is 100-200 ℃/s.
The sintering of the precursor of alumina in the present application is carried out in a roasting furnace.
Wherein the precursor of the alumina is aluminum hydroxide, including gibbsite, bayer stone, nordstrandite, boehmite and diaspore.
The application provides a preparation method of an alumina precursor, which comprises the following steps:
adding aluminum foil or aluminum powder and other aluminum with different forms into prepared alkyl ammonium hydroxide solution with certain concentration according to a certain liquid-solid ratio, and preparing a precursor with an aluminum hydroxide phase under the action of mechanical stirring and certain temperature.
The sintering temperature is 1000-1500 ℃, and the sintering time is 1-8 h.
In one embodiment of the present application, the sintering temperature of the precursor of alumina is 1200 ℃. In other embodiments of the present application, the sintering temperature of the precursor of alumina may also be 1000 ℃, 1050 ℃, 1100 ℃, 1150 ℃, 1200 ℃, 1250 ℃, 1300 ℃, 1350 ℃, 1400 ℃, 1450 ℃, or 1500 ℃.
In one embodiment of the present application, the sintering time of the precursor of alumina is 4 h. In other embodiments of the present application, the sintering time of the precursor of alumina may also be 1h, 2h, 3h, 5h, 6h, 7h, or 8 h.
The method for cooling the alumina powder to be below 20 ℃ at the cooling rate of 5-200 ℃/s comprises the step of mixing the alumina powder obtained by sintering with a reagent below 5 ℃ within 1-30 s of the sintering of the precursor of the alumina.
The alumina powder can be kept at about 1000-1500 ℃ within 1-30 s after sintering, and then the alumina powder obtained by sintering is quickly and uniformly mixed with a reagent below 5 ℃ so that the temperature of the alumina powder can be uniformly reduced to below 20 ℃ at a cooling rate of 5-200 ℃/s.
After the alumina powder which is sintered at the temperature of 1000-1500 ℃ is mixed with the reagent within 1-30 s, the reagent can fill the mesopores of the alumina powder, so that capillaries of part of the powder are opened or opened, collapse of the alumina powder is inhibited, and part of the micro-mesoporous structure is reduced.
The reagent comprises one or more of liquid nitrogen, dry ice, ice-water mixture, water with the temperature less than or equal to 5 ℃ and the balance of water.
The liquid nitrogen is liquid nitrogen, is inert, odorless, non-corrosive and non-flammable, has extremely low temperature of-200 to-140 ℃.
The dry ice is solid carbon dioxide, carbon dioxide gas is liquefied into colorless liquid under the pressure of 6250.5498 kPa, and then is rapidly solidified into carbon dioxide solid, namely the dry ice, the temperature of which is-90 to-60 ℃.
The ice-water mixture refers to a state in which ice and water are still present together after they are mixed together for a certain period of time under a standard atmospheric pressure, and this state serves as a temperature reference of 0 ℃.
The water with the temperature of less than or equal to 5 ℃ is liquid water with the temperature of less than or equal to 5 ℃ under the standard atmospheric pressure.
The liquid nitrogen and the dry ice can be volatilized at normal temperature, and impurities cannot be remained in the prepared alpha-alumina powder; the ice-water mixture and the water with the temperature less than or equal to 5 ℃ can be volatilized by a drying method, and impurities can not be remained in the prepared alpha-alumina powder.
Meanwhile, the liquid nitrogen, the dry ice, the ice water mixture and the water with the temperature less than or equal to 5 ℃ are nontoxic and low in price, and meet the requirements of environmental protection.
In one embodiment of the present application, the reagent is liquid nitrogen. In other embodiments of the present application, the reagent may also be dry ice, a mixture of ice and water or water with a temperature of less than or equal to 5 ℃, or may be a mixture of ice and water and dry ice, or may be a mixture of dry ice and water with a temperature of less than or equal to 5 ℃, or may be a mixture of dry ice, water and water with a temperature of less than or equal to 5 ℃.
The mass ratio of the alumina powder to the reagent is 1: 50-500.
When the required cooling rate is higher, the alumina powder with the same quality can be matched with reagents with more quality, and when the required cooling rate is lower, the alumina powder with the same quality can be matched with reagents with less quality. Certainly, the temperature reduction rate of the alumina powder is required to be ensured to be 5-200 ℃/s.
It is to be noted that, when the alumina powder is cooled by any one or more of dry ice, an ice-water mixture and water with the temperature of less than or equal to 5 ℃, the alumina powder is transferred to a container for containing a reagent. If transfer the reagent to the container that holds alumina powder in, can lead to partial alumina powder spill, have great potential safety hazard, will lead to alumina powder to be heated inhomogeneously simultaneously. When liquid nitrogen is adopted to cool the alumina powder, the liquid nitrogen is sprayed on the surface of the alumina powder containing body.
Optionally, the temperature reduction process of the alumina powder is performed in a metal or ceramic vessel.
Optionally, the temperature reduction process of the alumina powder is monitored in real time by an inductive coupling thermometer, so that the temperature reduction rate of the alumina powder is kept at 5-200 ℃/s when the temperature of the alumina powder is above 20 ℃.
And (3) taking out the alumina powder after the temperature of the alumina powder is reduced to below 20 ℃.
When the reagent is liquid nitrogen and/or dry ice, the liquid nitrogen and the dry ice can be volatilized under the conditions of normal temperature and normal pressure after the alumina powder is taken out.
When the reagent comprises an ice-water mixture and/or water with the temperature of less than or equal to 5 ℃, the water can be attached to the surface of the alumina powder, and then the alumina powder is dried for 2-8 hours at the temperature of 40-80 ℃. The drying can completely gasify the moisture in the alumina powder, and the pore structure of the prepared alpha-alumina is not influenced, namely the specific surface area of the prepared alpha-alumina is not reduced.
Optionally, before the alumina powder is dried, the mixture of the alumina powder and the reagent is filtered, the filter residue is retained, the alumina powder with a low water content can be obtained, and then the filter residue is dried, so that the drying time is reduced.
The application also provides alpha-alumina which is prepared according to the preparation method of the alpha-alumina.
The alpha-alumina prepared by the method has higher specific surface area of 10m2More than g, consistent powder morphology, good particle dispersibility and higher purity.
As shown in fig. 1, the pore size distribution of the α -alumina powder prepared by the present application is narrow, that is, the pore structure of the α -alumina powder obtained by rapid cooling is similar and single.
An α -alumina and a method for preparing the same according to the present application will be described in further detail with reference to examples.
Example 1
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
And pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with dry ice within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the dry ice is 1:50, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to below 20 ℃.
Example 2
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
And pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with dry ice within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the dry ice is 1:100, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to below 20 ℃.
Example 3
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
And pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with dry ice within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the dry ice is 1:300, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to below 20 ℃.
Example 4
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
And pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with dry ice within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the dry ice is 1:500, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to below 20 ℃.
Example 5
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic utensil within 30s after the alumina precursor is sintered, quickly spraying liquid nitrogen into the ceramic utensil, wherein the mass ratio of the alumina powder to the liquid nitrogen is 1:50, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to be below 20 ℃.
Example 6
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic utensil within 30s after the alumina precursor is sintered, quickly spraying liquid nitrogen into the ceramic utensil, wherein the mass ratio of the alumina powder to the liquid nitrogen is 1:100, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to be below 20 ℃.
Example 7
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic vessel within 30s after the alumina precursor is sintered, quickly spraying liquid nitrogen into the ceramic vessel, wherein the mass ratio of the alumina powder to the liquid nitrogen is 1:300, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to below 20 ℃.
Example 8
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic utensil within 30s after the alumina precursor is sintered, quickly spraying liquid nitrogen into the ceramic utensil, wherein the mass ratio of the alumina powder to the liquid nitrogen is 1:500, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to be below 20 ℃.
Example 9
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with an ice-water mixture within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the ice-water mixture is 1:50, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, taking out the mixture of the alumina powder and water after the temperature of the alumina powder is reduced to be below 20 ℃, filtering to obtain filter residue, and drying the filter residue in a drying oven with the temperature of 50 ℃ for 4h to obtain alpha-alumina.
Example 10
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
And pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with an ice-water mixture within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the ice-water mixture is 1:100, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to below 20 ℃.
Example 11
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with an ice-water mixture within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the ice-water mixture is 1:300, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, taking out the mixture of the alumina powder and water after the temperature of the alumina powder is reduced to be below 20 ℃, filtering to obtain filter residue, and drying the filter residue in a drying oven with the temperature of 50 ℃ for 4h to obtain alpha-alumina.
Example 12
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with an ice-water mixture within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the ice-water mixture is 1:500, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, taking out the mixture of the alumina powder and water after the temperature of the alumina powder is reduced to be below 20 ℃, filtering to obtain filter residue, and drying the filter residue in a drying oven with the temperature of 50 ℃ for 4h to obtain alpha-alumina.
Example 13
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic vessel filled with water with the temperature of 3 ℃ within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the water with the temperature of 3 ℃ is 1:50, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, taking out a mixture of the alumina powder and the water after the temperature of the alumina powder is reduced to be below 20 ℃, filtering to obtain filter residue, and drying the filter residue in a drying oven with the temperature of 50 ℃ for 4h to obtain the alpha-alumina.
Example 14
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic vessel filled with water with the temperature of 3 ℃ within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the water with the temperature of 3 ℃ is 1:100, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, taking out a mixture of the alumina powder and the water after the temperature of the alumina powder is reduced to be below 20 ℃, filtering to obtain filter residue, and drying the filter residue in a drying oven with the temperature of 50 ℃ for 4h to obtain the alpha-alumina.
Example 15
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic vessel filled with water with the temperature of 3 ℃ within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the water with the temperature of 3 ℃ is 1:300, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, taking out a mixture of the alumina powder and the water after the temperature of the alumina powder is reduced to be below 20 ℃, filtering to obtain filter residue, and drying the filter residue in a drying oven with the temperature of 50 ℃ for 4h to obtain the alpha-alumina.
Example 16
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic vessel filled with water with the temperature of 3 ℃ within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the water with the temperature of 3 ℃ is 1:500, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, taking out a mixture of the alumina powder and the water after the temperature of the alumina powder is reduced to be below 20 ℃, filtering to obtain filter residue, and drying the filter residue in a drying oven with the temperature of 50 ℃ for 4h to obtain the alpha-alumina.
Example 17
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
Will be alphak900g/L of active seed crystal of aluminum hydroxide was added to a sodium aluminate solution of 1.45 and caustic concentration of 155g/L, the seed crystal decomposition temperature was 55 ℃ and the reaction time was 40 hours. After the reaction is finished, the Bayer process-aluminium hydroxide can be obtained.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic vessel within 30s after the alumina precursor is sintered, quickly spraying liquid nitrogen into the ceramic vessel, wherein the mass ratio of the alumina powder to the liquid nitrogen is 1:300, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to below 20 ℃.
Example 18
The embodiment of the application provides alpha-alumina and a preparation method thereof, which comprises the following steps:
1. preparation of alumina precursor
And (2) mixing aluminum isopropoxide and pure water in a material ratio of 1: preparing an alkoxide mixed solution, and then putting the aluminum isopropoxide solution into a constant-temperature water bath kettle at 80 ℃ to continuously add water for 3 hours, so as to obtain an aluminum hydroxide precursor through hydrolysis.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic vessel within 30s after the alumina precursor is sintered, quickly spraying liquid nitrogen into the ceramic vessel, wherein the mass ratio of the alumina powder to the liquid nitrogen is 1:300, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to below 20 ℃.
Comparative example 1
The comparative example of the present application provides an alpha-alumina and a preparation method thereof, which includes the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
And pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with dry ice within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the dry ice is 1:30, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to below 20 ℃.
Comparative example 2
The comparative example of the present application provides an alpha-alumina and a preparation method thereof, which includes the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of more than 1000 ℃ obtained by sintering into a ceramic utensil within 30s after the alumina precursor is sintered, quickly spraying liquid nitrogen into the ceramic utensil, wherein the mass ratio of the alumina powder to the liquid nitrogen is 1:30, monitoring the cooling rate of the alumina powder in real time by adopting an inductive coupling thermometer, and obtaining alpha-alumina after the temperature of the alumina powder is reduced to be below 20 ℃.
Comparative example 3
The comparative example of the present application provides an alpha-alumina and a preparation method thereof, which includes the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with an ice-water mixture within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the ice-water mixture is 1:40, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, taking out the mixture of the alumina powder and water after the temperature of the alumina powder is reduced to be below 20 ℃, filtering to obtain filter residue, and drying the filter residue in a drying oven with the temperature of 50 ℃ for 4h to obtain alpha-alumina.
Comparative example 4
The comparative example of the present application provides an alpha-alumina and a preparation method thereof, which includes the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
Pouring the alumina powder with the temperature of over 1000 ℃ obtained by sintering into a ceramic vessel filled with water with the temperature of 15 ℃ within 30s after the sintering of the alumina precursor is completed, wherein the mass ratio of the alumina powder to the water with the temperature of 15 ℃ is 1:50, monitoring the cooling rate of the alumina powder in real time by using an inductive coupling thermometer, taking out a mixture of the alumina powder and the water after the temperature of the alumina powder is reduced to be below 20 ℃, filtering to obtain filter residue, and drying the filter residue in a drying oven with the temperature of 50 ℃ for 4h to obtain the alpha-alumina.
Comparative example 5
The comparative example of the present application provides an alpha-alumina and a preparation method thereof, which includes the following steps:
1. preparation of alumina precursor
Adding a certain amount of aluminum foil into an alkyl ammonium hydroxide solution with the concentration of 40g/L according to the liquid-solid ratio of 8:1, starting mechanical stirring at the stirring speed of 500r/min, reacting at the reaction temperature of 80 ℃ for 2 hours, and filtering and drying to obtain an aluminum oxide precursor, namely aluminum hydroxide.
2. Sintered alumina precursor
And placing the prepared alumina precursor in a muffle furnace, heating to 1200 ℃, and sintering for 4 h.
3. Preparation of alpha-alumina
After the sintering of the alumina precursor is finished, cooling the alumina powder with the temperature of more than 1000 ℃ obtained by sintering at room temperature, and obtaining the alpha-alumina after the temperature of the alumina powder is reduced to be less than 20 ℃.
Test example 1
The average cooling rates of examples 1 to 18 and comparative examples 1 to 5, and the specific surface area, particle size, pore volume, pore diameter and phase of the obtained α -alumina were measured, respectively, as shown in table 1.
TABLE 1 average Cooling Rate of examples 1 to 18 and comparative examples 1 to 5 and specific surface area, particle size, pore volume, pore diameter and phase of the alpha-alumina produced
From examples 1 to 18, it is understood that the specific surface area of the α -alumina prepared by the method for preparing α -alumina of the present application is 10 to 40m2(g), except that the effect of water at 3 ℃ as a refrigerant is slightly poor, the specific surface area of alpha-alumina obtained by using an ice-water mixture and liquid nitrogen of dry ice as the refrigerant reaches 20m2More than g.
Comparing comparative example 1 with examples 1-4, it can be seen that the mass ratio of the alumina powder to the dry ice is 1:30, which results in the insufficient cooling rate of the alumina powder and the small specific surface area of the prepared alpha-alumina.
As shown in comparison of comparative example 2 and examples 5-8, the mass ratio of the alumina powder to the liquid nitrogen is 1:30, so that the cooling rate of the alumina powder is not fast enough, and the specific surface area of the prepared alpha-alumina is small.
As can be seen from comparison of comparative example 3 with examples 9 to 12, the mass ratio of the alumina powder to the ice-water mixture is 1:40, so that the cooling rate of the alumina powder is not fast enough, and the specific surface area of the prepared alpha-alumina is small.
Comparison of comparative example 4 with example 13 shows that the cooling rate of the alumina powder is not fast enough due to the fact that the refrigerant is water at 15 ℃, and the specific surface area of the prepared alpha-alumina is small.
In summary, the embodiments of the present application provide a method for preparing α -alumina, in which a rapid cooling method is adopted to reduce a part of alumina pore structures, during a rapid cooling process of alumina powder, capillaries in the alumina powder are opened, collapse of the pore structures is suppressed, and finally a part of micro-mesoporous structures can be reduced, so that a specific surface area of the prepared α -alumina is improved to a certain extent. In the reagent adopted in the cooling process, liquid nitrogen and dry ice can volatilize at normal temperature, and impurities cannot be remained in the prepared alpha-alumina powder; the ice-water mixture and the water with the temperature less than or equal to 5 ℃ can be volatilized by a drying method, and impurities can not be remained in the prepared alpha-alumina powder. The whole preparation process is simple and convenient and is easy to control. The alpha-alumina prepared by the method has stable performance and the specific surface area of the alpha-alumina is 10m2More than g, consistent powder morphology, good particle dispersibility and higher purity.
The foregoing is illustrative of the present application and is not to be construed as limiting thereof, as numerous modifications and variations will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (9)
1. A method for preparing alpha-alumina, which is characterized by comprising the following steps: after sintering of the precursor of the alumina, mixing the alumina powder with 1000-1500 ℃ obtained by sintering with a reagent with the temperature of below 5 ℃ within 1-30 s of the sintering of the precursor of the alumina, and cooling the alumina powder to below 20 ℃ at the cooling rate of 5-200 ℃/s.
2. The method for preparing alpha-alumina according to claim 1, wherein the mass ratio of the alumina powder to the reagent is 1:50 to 500.
3. The method for preparing alpha-alumina according to claim 1, wherein the reagent comprises any one or more of liquid nitrogen, dry ice, ice-water mixture and water with temperature less than or equal to 5 ℃.
4. The method for preparing alpha-alumina according to claim 3, wherein the temperature of the liquid nitrogen is-200 to-140 ℃ and the temperature of the dry ice is-90 to-60 ℃.
5. The preparation method of alpha-alumina according to claim 3, wherein the reagent comprises the ice-water mixture and/or the water with the temperature of less than or equal to 5 ℃, and the alumina powder is dried for 2-8 hours at 40-80 ℃ after the temperature of the alumina powder is reduced to below 20 ℃.
6. The preparation method of alpha-alumina according to claim 5, wherein the mixture of the alumina powder and the reagent is filtered before the alumina powder is dried at 40-80 ℃ for 2-8 hours, and filter residue is retained.
7. The method for preparing alpha-alumina according to any one of claims 1 to 6, wherein the temperature reduction rate of the alumina powder is monitored in real time by an inductively coupled thermometer.
8. The method for producing α -alumina according to any one of claims 1 to 6, wherein the sintering temperature of the precursor of alumina is 1000 to 1500 ℃ and the sintering time is 1 to 8 hours.
9. An alpha-alumina prepared by the method according to any one of claims 1 to 8.
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| US4752459A (en) * | 1985-04-09 | 1988-06-21 | Perrer Duncan S | Preparation of porous bodies |
| CN101516782A (en) * | 2006-09-19 | 2009-08-26 | 住友化学株式会社 | Alpha-alumina powder |
| CN102020298A (en) * | 2010-10-26 | 2011-04-20 | 天津大学 | Al2O3 with double mesoporous distribution and its preparation method |
| JP2011102215A (en) * | 2009-11-11 | 2011-05-26 | Denki Kagaku Kogyo Kk | Spherical alumina powder, and production method and application of the same |
| CN105540630A (en) * | 2015-12-09 | 2016-05-04 | 靖江市晨阳化工有限公司 | Preparation method of catalyst carrier for glycol prepared from coal |
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| US4752459A (en) * | 1985-04-09 | 1988-06-21 | Perrer Duncan S | Preparation of porous bodies |
| CN101516782A (en) * | 2006-09-19 | 2009-08-26 | 住友化学株式会社 | Alpha-alumina powder |
| JP2011102215A (en) * | 2009-11-11 | 2011-05-26 | Denki Kagaku Kogyo Kk | Spherical alumina powder, and production method and application of the same |
| CN102020298A (en) * | 2010-10-26 | 2011-04-20 | 天津大学 | Al2O3 with double mesoporous distribution and its preparation method |
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