CN110512310B - Preparation method of micron-scale alumina fiber - Google Patents
Preparation method of micron-scale alumina fiber Download PDFInfo
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- CN110512310B CN110512310B CN201910828533.1A CN201910828533A CN110512310B CN 110512310 B CN110512310 B CN 110512310B CN 201910828533 A CN201910828533 A CN 201910828533A CN 110512310 B CN110512310 B CN 110512310B
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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 74
- 239000000835 fiber Substances 0.000 title claims abstract description 30
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 229910001593 boehmite Inorganic materials 0.000 claims abstract description 69
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims abstract description 68
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 29
- 239000002243 precursor Substances 0.000 claims abstract description 29
- 238000005245 sintering Methods 0.000 claims abstract description 21
- 239000000654 additive Substances 0.000 claims abstract description 19
- 230000000996 additive effect Effects 0.000 claims abstract description 19
- 238000010335 hydrothermal treatment Methods 0.000 claims abstract description 6
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 36
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 33
- 239000000843 powder Substances 0.000 claims description 31
- 238000003756 stirring Methods 0.000 claims description 21
- WOZZOSDBXABUFO-UHFFFAOYSA-N tri(butan-2-yloxy)alumane Chemical compound [Al+3].CCC(C)[O-].CCC(C)[O-].CCC(C)[O-] WOZZOSDBXABUFO-UHFFFAOYSA-N 0.000 claims description 20
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 18
- 229910017604 nitric acid Inorganic materials 0.000 claims description 18
- 238000006243 chemical reaction Methods 0.000 claims description 16
- 239000007864 aqueous solution Substances 0.000 claims description 14
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 14
- 239000000243 solution Substances 0.000 claims description 11
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- 239000007787 solid Substances 0.000 claims description 9
- IRPGOXJVTQTAAN-UHFFFAOYSA-N 2,2,3,3,3-pentafluoropropanal Chemical compound FC(F)(F)C(F)(F)C=O IRPGOXJVTQTAAN-UHFFFAOYSA-N 0.000 claims description 8
- KLZUFWVZNOTSEM-UHFFFAOYSA-K Aluminum fluoride Inorganic materials F[Al](F)F KLZUFWVZNOTSEM-UHFFFAOYSA-K 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- 238000010992 reflux Methods 0.000 claims description 8
- 230000003301 hydrolyzing effect Effects 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 6
- -1 polytetrafluoroethylene Polymers 0.000 claims description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 4
- WRMFBHHNOHZECA-UHFFFAOYSA-N butan-2-olate Chemical compound CCC(C)[O-] WRMFBHHNOHZECA-UHFFFAOYSA-N 0.000 claims description 4
- 239000008367 deionised water Substances 0.000 claims description 4
- 229910021641 deionized water Inorganic materials 0.000 claims description 4
- 230000007062 hydrolysis Effects 0.000 claims description 4
- 238000006460 hydrolysis reaction Methods 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 239000000178 monomer Substances 0.000 claims description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 4
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 4
- 238000007789 sealing Methods 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- 239000002073 nanorod Substances 0.000 abstract description 18
- 238000000034 method Methods 0.000 abstract description 12
- 238000010438 heat treatment Methods 0.000 abstract description 6
- 230000015572 biosynthetic process Effects 0.000 abstract 1
- 238000012360 testing method Methods 0.000 description 26
- 239000002105 nanoparticle Substances 0.000 description 11
- 238000001878 scanning electron micrograph Methods 0.000 description 8
- 238000010521 absorption reaction Methods 0.000 description 7
- 239000002245 particle Substances 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
- 229910002706 AlOOH Inorganic materials 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 238000005452 bending Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 3
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- BTANRVKWQNVYAZ-UHFFFAOYSA-N butan-2-ol Chemical compound CCC(C)O BTANRVKWQNVYAZ-UHFFFAOYSA-N 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 239000010431 corundum Substances 0.000 description 2
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052863 mullite Inorganic materials 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 235000012431 wafers Nutrition 0.000 description 2
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 229910018516 Al—O Inorganic materials 0.000 description 1
- 229910003849 O-Si Inorganic materials 0.000 description 1
- 238000001016 Ostwald ripening Methods 0.000 description 1
- 229910003872 O—Si Inorganic materials 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000004323 axial length Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000012784 inorganic fiber Substances 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 239000004005 microsphere Substances 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 230000000877 morphologic effect Effects 0.000 description 1
- 239000002060 nanoflake Substances 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
- 230000010494 opalescence Effects 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 229910006636 γ-AlOOH Inorganic materials 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- 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
- C01F7/30—Preparation of aluminium oxide or hydroxide by thermal decomposition or by hydrolysis or oxidation of aluminium compounds
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
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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
- C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
- C01P2004/16—Nanowires or nanorods, i.e. solid nanofibres with two nearly equal dimensions between 1-100 nanometer
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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
- C01P2004/54—Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
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- Engineering & Computer Science (AREA)
- Nanotechnology (AREA)
- Physics & Mathematics (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Thermal Sciences (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Crystallography & Structural Chemistry (AREA)
- Geology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Textile Engineering (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
A preparation method of micron-grade alumina fiber, relating to a preparation method of alumina fiber. The invention aims to solve the technical problem that the length-diameter ratio of the existing particle-shaped alumina is lower after heat treatment, and the alumina fiber is prepared by high-temperature sintering. The invention comprises the following steps: firstly, preparing an alumina precursor; secondly, performing hydrothermal treatment; and thirdly, sintering. The method comprises the steps of firstly preparing an alumina precursor by adopting a sol method, then preparing boehmite nanorods by adopting a hydrothermal method, and then sintering the boehmite nanorods at a high temperature to prepare the alumina fiber. Among them, the proper amount of the additive and the subsequent heat treatment process are the most critical factors for the formation of one-dimensional structure of alumina during the preparation process. The method is based on a hydrothermal method to prepare the nano boehmite rod with higher length-diameter ratio, and prepares the micron alumina fiber through high-temperature sintering, and has the advantages of simple process, controllable product morphology, high purity and wide prospect.
Description
Technical Field
The invention relates to a preparation method of alumina fiber.
Background
Alumina (Al)2O3) The fiber is a novel polycrystalline high-performance inorganic fiber, generally has higher tensile strength, good electrical insulation performance, better elastic modulus and oxidation resistance, and has oxidation reduction performanceCan keep good chemical stability in the atmosphere; meanwhile, the composite material also has the advantages of low thermal conductivity and thermal expansion coefficient, good thermal shock resistance and the like, so that the composite material is widely applied to the fields of aerospace, industrial high-temperature heat preservation and insulation, high-temperature filtration, organic and heavy metal ion adsorbents, catalyst carriers and the like.
Boehmite (boehmite), also known as boehmite, is an oxide of aluminum, has a molecular formula of γ -AlOOH, has a layered structure, and is a precursor of many aluminum-containing oxides. The boehmite system inherits the good heat insulation and flame retardant properties of the aluminum oxide system, has good compatibility with various substances and good adsorption property, and can be widely applied to catalyst carriers, films, coatings, absorbents or light-transmitting materials. Boehmite can present different micro-morphological characteristics according to different preparation processes, such as one-dimensional nano rods or nano tubes, two-dimensional nano flakes, three-dimensional hollow spheres, flower-like (flowerlike) or Hami melon-like. The one-dimensional nano rod-shaped boehmite has excellent mechanical, chemical and mechanical properties due to the special structural characteristics, and is a material which is richest in research prospect and expansion space. Boehmite is generally converted to alumina after heat treatment. Hydrothermal method is a common method for synthesizing nano-boehmite rods. The method can prepare the boehmite nano-rod with higher length-diameter ratio. However, under different hydrothermal conditions, boehmite grows into a series of different morphologies such as a band shape, a rod shape, a needle shape, a sheet shape, and the like. Researches show that boehmite is easy to grow along a certain specific direction by adjusting the solution environment of a system, so that a boehmite nanorod structure with a high length-diameter ratio can be obtained, and high-performance micron-grade alumina fibers are prepared by high-temperature sintering. This micron-sized alumina fiber has the potential to constitute an alumina fibrous thermal insulation material. The conventional particulate alumina has a long length in one dimension after heat treatment, but generally has a relatively low length-diameter ratio.
Disclosure of Invention
The invention provides a preparation method of micron-grade alumina fiber, aiming at solving the technical problem that the length-diameter ratio of the existing particle-shaped alumina after heat treatment is lower.
The preparation method of the micron-scale alumina fiber is carried out according to the following steps:
firstly, preparing an alumina precursor: mixing aluminum sec-butoxide with water, refluxing and stirring for 1-1.5 h under the water bath condition of 70-100 ℃ to dissolve the aluminum sec-butoxide in the water and hydrolyzing to generate an active monomer, then adding a dilute nitric acid aqueous solution to promote further hydrolysis, wherein the solution is clarified from milky color, then continuously refluxing and stirring for 9-12 h under the water bath condition of 70-100 ℃ to obtain alumina hydrosol, putting the alumina hydrosol into a constant-temperature stirring heater of 100-110 ℃, removing the sec-butoxide and the nitric acid until the content of Al element in the sol is 1-1.1 mol/L, and obtaining the sol which is an alumina precursor;
the molar ratio of the aluminum sec-butoxide to the water is 0.12 (9.5-10);
the mass ratio of the dilute nitric acid aqueous solution to the secondary aluminum butoxide is 1 (6-7);
secondly, hydrothermal treatment: placing the alumina precursor obtained in the step one in a reaction kettle made of polytetrafluoroethylene, adding an additive, uniformly stirring, sealing the reaction kettle, carrying out hydrothermal reaction, washing with water and centrifuging for three times after the hydrothermal reaction is finished to obtain a white gelatinous solid, and drying the white gelatinous solid in a drying box at 60-65 ℃ for 12-13 h to obtain boehmite rod powder, wherein the alumina precursor accounts for 75-85% of the volume of the reaction kettle; the temperature of the hydrothermal reaction is 140-220 ℃, and the time of the hydrothermal reaction is 1-8 days; the volume ratio of the additive in the step two to the alumina precursor sol obtained in the step one is 1 (3.5-80);
thirdly, high-temperature sintering: adding aluminum fluoride and silica sol into the boehmite rod powder obtained in the step two, uniformly stirring, and then putting into a muffle furnace for sintering treatment to obtain micron-grade alumina fibers; the sintering temperature is 800-1400 ℃, and the heat preservation time is 1-4 h;
the mass ratio of the boehmite rod powder obtained in the second step to the aluminum fluoride is 1 (0.3-0.5);
and the mass ratio of the boehmite rod powder obtained in the second step to the silica sol is 1 (0.016-0.16).
The principle of the invention is as follows:
the addition of acetic acid as an additive in the invention provides an acidic environment for the solution, wherein the pH of the solution is 2-5, and Al (OH) in the solution is obtained2+And Al (OH)2 +At a higher concentration, the surface hydroxyl groups of the boehmite are replaced by OH2+The form exists. CH (CH)3COO–As a small molecular shape direction control agent, the control of the growth direction of the boehmite crystal can be realized. Since the hydroxyl groups of the (010) and (001) planes have an effect of adsorbing acidic ions through hydrogen bonds, CH3COO-Can be selectively absorbed on (010) and (001) surfaces to limit gamma-AlOOH particles to [ 010%]And [001]]Directional growth, thereby causing the boehmite particles to preferentially follow [100]]The directions are gathered. In this case, the particles are easily aggregated into large clusters along the longer axis, and directionally aggregated to form boehmite nanorods.
The hydrothermal method has the characteristics of simple process, small pollution, high product purity, good crystallinity and the like, is a common method for synthesizing the nano boehmite rod, and can prepare the boehmite nano rod with higher length-diameter ratio and good crystallization. The invention is based on a hydrothermal method, and takes aluminum sec-butoxide (ASB) as an aluminum source to prepare the alumina fiber. The method comprises the steps of firstly preparing an alumina precursor by adopting a sol method, then preparing boehmite nanorods by adopting a hydrothermal method, and then preparing alumina fibers by high-temperature sintering. Wherein, in the preparation process, the proper additive dosage is the most critical factor for the alumina to form a one-dimensional structure.
Several inventive points of the present application are as follows:
(1) in the step one, the alumina hydrosol is put into a constant-temperature stirring heater at 100-110 ℃ to remove sec-butyl alcohol and nitric acid until the content of Al element in the sol is 1-1.1 mol/L, and the sol obtained at the moment is an alumina precursor;
(2) in the second step, "the alumina precursor accounts for 75% -85% of the volume of the reaction kettle", the volume of the alumina precursor solution in the reaction kettle is limited, the pressure in the reaction kettle is actually ensured to be a determined value during hydrothermal treatment, and under the pressure, the one-dimensional directional growth of the boehmite nanorods is facilitated;
(3) the acid anions in step two can be selectively adsorbed on the (010) and (001) faces of boehmite, which limits the aggregation of boehmite particles on the faces, resulting in the tendency of boehmite particles to aggregate in the [100] direction. In the case of the additive acetic acid, the acid groups of acetic acid are readily adsorbed on the surfaces of the boehmite particles. Meanwhile, in the hydrothermal process, boehmite crystals grow in the directions of [100] and [010] in an Ostwald ripening mode. In the hydrothermal process, along with the prolonging of hydrothermal time, the acetate is desorbed from the surface of boehmite relatively slowly, the growth of the boehmite along the [010] and [001] directions can be limited, and one-dimensional boehmite morphological characteristics with a certain length-diameter ratio are formed. In addition, compared with inorganic acid, such as hydrochloric acid, sulfuric acid, nitric acid and the like, organic acid acetic acid molecules are easy to remove in subsequent heat treatment, and the purity of the alumina fiber can be ensured;
(4) and a small amount of silica sol added in the third step participates in the reaction, Al-O-Al bonds are broken to generate Al-O-Si bonds, and the growth speed of the aluminum oxide along a certain crystal direction is accelerated and the aluminum oxide gradually grows into micron-sized fibers.
The invention has the advantages that:
the preparation method disclosed by the invention is used for preparing the nano boehmite rod with a higher length-diameter ratio (50-70) based on a hydrothermal method, and preparing the micron alumina fiber through high-temperature sintering, and has the advantages of simple process, controllable product morphology, high purity and wide prospect.
Drawings
FIG. 1 is a FT-IR plot of a nano-sized boehmite rod powder prepared according to test one;
figure 2 is an XRD pattern of a nano-sized boehmite rod powder prepared according to experiment one;
FIG. 3 is a TEM image of a nano-sized boehmite rod powder prepared according to run one;
FIG. 4 is an SEM image of a nanoscale boehmite rod powder prepared by run three;
FIG. 5 is an SEM image of nano-sized boehmite rod powder prepared by run two;
FIG. 6 is an SEM image of micron grade alumina fibers made in run two;
FIG. 7 is an XRD pattern of micron grade alumina fibers prepared in run two;
figure 8 is an SEM image of nano-sized boehmite rod powder prepared by run four.
Detailed Description
The first embodiment is as follows: the embodiment is a preparation method of a nano-scale boehmite rod, which is specifically carried out according to the following steps:
firstly, preparing an alumina precursor: mixing aluminum sec-butoxide with water, refluxing and stirring for 1-1.5 h under the water bath condition of 70-100 ℃ to dissolve the aluminum sec-butoxide in the water and hydrolyzing to generate an active monomer, then adding a dilute nitric acid aqueous solution to promote further hydrolysis, wherein the solution is clarified by opalescence, then continuously refluxing and stirring for 9-12 h under the water bath condition of 70-100 ℃ to obtain alumina hydrosol, putting the alumina hydrosol into a constant-temperature stirring heater of 100-110 ℃, removing the sec-butoxide and the nitric acid until the content of Al element in the sol is 1-1.1 mol/L, and obtaining the sol which is an alumina precursor;
the molar ratio of the aluminum sec-butoxide to the water is 0.12 (9.5-10);
the mass ratio of the dilute nitric acid aqueous solution to the secondary aluminum butoxide is 1 (6-7);
secondly, hydrothermal treatment: placing the alumina precursor obtained in the step one in a reaction kettle made of polytetrafluoroethylene, adding an additive, uniformly stirring, sealing the reaction kettle, carrying out hydrothermal reaction, washing with water and centrifuging for three times after the hydrothermal reaction is finished to obtain a white gelatinous solid, and drying the white gelatinous solid in a drying box at 60-65 ℃ for 12-13 h to obtain boehmite rod powder, wherein the alumina precursor accounts for 75-85% of the volume of the reaction kettle; the temperature of the hydrothermal reaction is 140-220 ℃, and the time of the hydrothermal reaction is 1-8 days;
the volume ratio of the additive in the second step to the alumina precursor sol obtained in the first step is 1 (3.5-80).
Thirdly, high-temperature sintering: adding aluminum fluoride and silica sol into the boehmite rod powder obtained in the step two, uniformly stirring, and then putting into a muffle furnace for sintering treatment to obtain micron-grade alumina fibers; the sintering temperature is 800-1400 ℃, and the heat preservation time is 1-4 h;
the mass ratio of the boehmite rod powder obtained in the second step to the aluminum fluoride is 1 (0.3-0.5);
and the mass ratio of the boehmite rod powder obtained in the second step to the silica sol is 1 (0.016-0.16).
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the concentration of the dilute nitric acid aqueous solution in the step one is 1 mol/L. The rest is the same as the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the molar ratio of the aluminum sec-butoxide to the water in step one is 0.12: 9.7. The others are the same as in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: the mass ratio of the volume of the dilute nitric acid aqueous solution to the aluminum sec-butoxide in the step one is 1: 6. The rest is the same as one of the first to third embodiments.
The fifth concrete implementation mode: the fourth difference between this embodiment and the specific embodiment is that: the additive in the second step is acetic acid which is a pure substance. The rest is the same as the fourth embodiment.
The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is: and in the second step, the white gelatinous solid is put into an oven at 60 ℃ to be dried for 12 hours. The rest is the same as one of the first to fifth embodiments.
The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the temperature of the hydrothermal reaction in the second step is 160 ℃, and the time of the hydrothermal reaction is 2 days. The rest is the same as one of the first to sixth embodiments.
The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: the sintering temperature in the third step is 1200 ℃, and the heat preservation time is 2 hours. The rest is the same as one of the first to seventh embodiments.
The invention was verified with the following tests:
test one: the test is a preparation method of the nano boehmite rod, and is specifically carried out according to the following steps:
firstly, preparing an alumina precursor: mixing aluminum sec-butoxide with water, refluxing and stirring for 1h under the condition of a water bath at 90 ℃ to dissolve the aluminum sec-butoxide in the water and hydrolyzing to generate an active monomer, then adding a dilute nitric acid aqueous solution to promote further hydrolysis, wherein the solution turns from milky white to clear, then continuously refluxing and stirring for 9h under the condition of the water bath at 90 ℃ to obtain alumina hydrosol, putting the alumina hydrosol into a constant-temperature stirring heater at 100 ℃, removing the sec-butoxide and the nitric acid until the content of Al element in the sol is 1mol/L, and obtaining the sol which is an alumina precursor;
the concentration of the dilute nitric acid aqueous solution in the step one is 1 mol/L;
the molar ratio of the aluminum sec-butoxide to the water is 0.12: 9.7;
the mass ratio of the dilute nitric acid aqueous solution to the aluminum sec-butoxide is 1: 6;
secondly, hydrothermal treatment: placing the alumina precursor obtained in the step one in a reaction kettle made of polytetrafluoroethylene, adding an additive, uniformly stirring, sealing the reaction kettle, carrying out hydrothermal reaction, washing with water and centrifuging for three times after the hydrothermal reaction is finished to obtain a white gelatinous solid, and drying the white gelatinous solid in a drying box at 60 ℃ for 12 hours to obtain boehmite rod powder, wherein the alumina precursor accounts for 80% of the volume of the reaction kettle; the temperature of the hydrothermal reaction is 160 ℃, and the time of the hydrothermal reaction is 2 days; the additive in the second step is acetic acid;
the volume ratio of the additive in the step two to the alumina precursor sol obtained in the step one is 1: 26.7;
thirdly, high-temperature sintering: adding aluminum fluoride and silica sol into the boehmite rod powder obtained in the step two, uniformly stirring, and then putting into a muffle furnace for sintering treatment to obtain micron-grade alumina fiber powder; the sintering temperature is 1200 ℃, and the heat preservation time is 2 hours;
the mass ratio of the boehmite rod powder obtained in the second step to the aluminum fluoride is 1: 0.3;
the mass ratio of the boehmite rod powder obtained in the second step to the silica sol is 1: 0.03;
the preparation method of the silica sol comprises the following steps: adding absolute ethyl alcohol into tetraethoxysilane, then adding deionized water and 0.2mol/L hydrochloric acid aqueous solution, and hydrolyzing in a water bath at 45 ℃ for 2 hours to obtain silica sol; ethyl orthosilicate: anhydrous ethanol: deionized water: the mass ratio of 0.2mol/L aqueous hydrochloric acid solution was 1:0.88:0.35: 0.01.
FIG. 1 is a FT-IR chart of a nano-sized boehmite rod powder prepared in the first two-stage test, from which it can be seen that the wave number is 500cm-1～750cm-1Is an aluminum hexahedron coordinated vibration absorption peak of 745cm-1、640cm-1、476cm-1Respectively corresponding to the torsional vibration, the telescopic vibration and the bending vibration of the Al-O; 1159cm-1The asymmetric bending vibration absorption peak of an O-H bond in AlOOH is positioned; 1070cm-1Is located at 1627cm, which is a bending vibration absorption peak of O-H bond in AlOOH-1The O-H bending vibration absorption peak of water is positioned; 3298cm-1The vibration absorption peak is an asymmetric stretching vibration absorption peak of O-H in an AlOOH structure, and is 3089cm-1The position is an O-H symmetric stretching vibration absorption peak in an AlOOH structure.
Fig. 2 is an XRD pattern of the nano-sized boehmite rod powder prepared in the first step and the second step of the experiment, and the test result shows that the hydrothermal product contains only boehmite crystals, belongs to an orthorhombic system, has a Cmcm space group structure, and is consistent with a boehmite standard spectrum (PDF card No. 83-2384). Meanwhile, no diffraction peak of other impurities is found in the test result, so that the purity of the obtained boehmite sample is high.
FIG. 3 is a TEM image of the nano-sized boehmite rod powder prepared in the first step two of the experiment, from which it can be seen that the axial length of the sample is between 200nm and 400nm, but the edges of the nanorods are not smooth and have a distinct nodular structure. The shape of the nano-rod is uniform, and the long and short dimension of the nano-rod has small dispersity.
And (2) test II: this test differs from the test one in that: the hydrothermal reaction time in the second step is 1 day, and the volume ratio of the additive in the second step to the alumina precursor sol obtained in the first step is 1: 8. The rest is the same as test one.
FIG. 7 is the XRD pattern of the micron-sized alumina fiber prepared in test two, wherein 1 is corundum, 2 is mullite, from which it can be seen that the sample has diffraction peaks at 2 theta 25.58 °, 35.15 °, 37.78 °, 43.36 ° and 57.5 °, and the product is corundum (hexagonal system alpha-Al) by comparing with PDF 74-1081 standard card2O3) In addition, it contains a mullite phase formed between the silica sol and the alumina introduced. The diffraction peaks of the sample are sharp peaks, and the peak width is small, which shows that the crystal grain size is large and the crystallinity is strong.
And (3) test III: this test is a comparative test, unlike test two, no additive was added in step two. The rest was the same as in test two.
And (4) testing: the test is a comparative test, and is different from the second test in that the volume ratio of the additive in the second step to the alumina precursor sol obtained in the first step is 3: 8. The rest was the same as in test two.
Fig. 4 is an SEM image of the nano-sized boehmite rod powder prepared in the second test three-step, fig. 5 is an SEM image of the nano-sized boehmite rod powder prepared in the second test two-step, fig. 6 is an SEM image of the micro-sized alumina fiber powder prepared in the second test two-step, and fig. 8 is an SEM image of the nano-sized boehmite rod powder prepared in the second test four-step, and it can be seen from the images that the length of boehmite nanorods has a very significant correlation with the acetic acid content. When acetic acid was not added during the hydrothermal process (fig. 4), the boehmite nanorods showed only a tendency to grow in one-dimensional direction, and the length thereof was only in the range of 200nm to 300 nm. When acetic acid is added, the length of the nano rod is improved by an order of magnitude, the length of the nano rod can be between 1.5 and 2 mu m, the width of the nano rod is not changed greatly, the average diameter is about 30nm, the length-diameter ratio is between 50 and 70 (figure 5), the alumina fiber prepared by high-temperature sintering grows in a radial mode, and the average length of the alumina fiber is about 200 mu m (figure 6). However, excessive addition of the additive affects the aggregation state between boehmites, and the nanorods extending out of the surface of the sample are bent and aggregated together. When the content of acetic acid is further increased, the one-dimensional growth tendency of boehmite gradually becomes gentle at this time, thicker plate-like wafers are formed, and these thicker plate-like wafers aggregate to form microspheres of about 10 μm (fig. 8). The proper amount of acetic acid is therefore the most critical factor for the boehmite to form a one-dimensional structure.
Claims (1)
1. A preparation method of micron-scale alumina fiber is characterized in that the preparation method of the micron-scale alumina fiber is carried out according to the following steps:
firstly, preparing an alumina precursor: mixing aluminum sec-butoxide with water, refluxing and stirring for 1h under the condition of a water bath at 90 ℃ to dissolve the aluminum sec-butoxide in the water and hydrolyzing to generate an active monomer, then adding a dilute nitric acid aqueous solution to promote further hydrolysis, wherein the solution turns from milky white to clear, then continuously refluxing and stirring for 9h under the condition of the water bath at 90 ℃ to obtain alumina hydrosol, putting the alumina hydrosol into a constant-temperature stirring heater at 100 ℃, removing the sec-butoxide and the nitric acid until the content of Al element in the sol is 1mol/L, and obtaining the sol which is an alumina precursor;
the concentration of the dilute nitric acid aqueous solution in the step one is 1 mol/L;
the molar ratio of the aluminum sec-butoxide to the water is 0.12: 9.7;
the mass ratio of the dilute nitric acid aqueous solution to the aluminum sec-butoxide is 1: 6;
secondly, hydrothermal treatment: placing the alumina precursor obtained in the step one in a reaction kettle made of polytetrafluoroethylene, adding an additive, uniformly stirring, sealing the reaction kettle, carrying out hydrothermal reaction, washing with water and centrifuging for three times after the hydrothermal reaction is finished to obtain a white gelatinous solid, and drying the white gelatinous solid in a drying box at 60 ℃ for 12 hours to obtain boehmite rod powder, wherein the alumina precursor accounts for 80% of the volume of the reaction kettle; the temperature of the hydrothermal reaction is 160 ℃, and the time of the hydrothermal reaction is 2 days; the additive in the second step is acetic acid;
the volume ratio of the additive in the step two to the alumina precursor sol obtained in the step one is 1: 8;
thirdly, high-temperature sintering: adding aluminum fluoride and silica sol into the boehmite rod powder obtained in the step two, uniformly stirring, and then putting into a muffle furnace for sintering treatment to obtain micron-grade alumina fiber powder; the sintering temperature is 1200 ℃, and the heat preservation time is 2 hours;
the mass ratio of the boehmite rod powder obtained in the second step to the aluminum fluoride is 1: 0.3;
the mass ratio of the boehmite rod powder obtained in the second step to the silica sol is 1: 0.03;
the preparation method of the silica sol comprises the following steps: adding absolute ethyl alcohol into tetraethoxysilane, then adding deionized water and 0.2mol/L hydrochloric acid aqueous solution, and hydrolyzing in a water bath at 45 ℃ for 2 hours to obtain silica sol; ethyl orthosilicate: anhydrous ethanol: deionized water: the mass ratio of 0.2mol/L aqueous hydrochloric acid solution was 1:0.88:0.35: 0.01.
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