CN112960681A - Method for preparing self-assembled hollow alumina microspheres by using sesbania gum as template - Google Patents
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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 64
- 238000000034 method Methods 0.000 title claims abstract description 40
- 239000004005 microsphere Substances 0.000 title claims abstract description 32
- 244000275012 Sesbania cannabina Species 0.000 title 1
- 239000007787 solid Substances 0.000 claims abstract description 39
- 241000219782 Sesbania Species 0.000 claims abstract description 27
- 239000000203 mixture Substances 0.000 claims abstract description 25
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000001035 drying Methods 0.000 claims abstract description 16
- 238000003756 stirring Methods 0.000 claims abstract description 16
- 238000005406 washing Methods 0.000 claims abstract description 16
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims abstract description 10
- QGBSISYHAICWAH-UHFFFAOYSA-N dicyandiamide Chemical compound NC(N)=NC#N QGBSISYHAICWAH-UHFFFAOYSA-N 0.000 claims abstract description 10
- SKFYTVYMYJCRET-UHFFFAOYSA-J potassium;tetrafluoroalumanuide Chemical compound [F-].[F-].[F-].[F-].[Al+3].[K+] SKFYTVYMYJCRET-UHFFFAOYSA-J 0.000 claims abstract description 10
- 238000001132 ultrasonic dispersion Methods 0.000 claims abstract description 10
- AMVQGJHFDJVOOB-UHFFFAOYSA-H aluminium sulfate octadecahydrate Chemical compound O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.[Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O AMVQGJHFDJVOOB-UHFFFAOYSA-H 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 239000008367 deionised water Substances 0.000 claims abstract description 7
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 7
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 238000009777 vacuum freeze-drying Methods 0.000 claims abstract description 5
- 238000010438 heat treatment Methods 0.000 claims description 33
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 32
- 238000006243 chemical reaction Methods 0.000 claims description 21
- 230000035484 reaction time Effects 0.000 claims description 12
- 239000000126 substance Substances 0.000 claims description 12
- 230000008569 process Effects 0.000 claims description 11
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 8
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 8
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 8
- 238000007710 freezing Methods 0.000 claims description 6
- 230000008014 freezing Effects 0.000 claims description 6
- 238000000926 separation method Methods 0.000 claims description 3
- 238000004108 freeze drying Methods 0.000 claims description 2
- 239000013078 crystal Substances 0.000 abstract description 17
- 238000004519 manufacturing process Methods 0.000 abstract description 14
- 238000004321 preservation Methods 0.000 abstract 1
- 238000002360 preparation method Methods 0.000 description 10
- 238000001556 precipitation Methods 0.000 description 9
- 239000003795 chemical substances by application Substances 0.000 description 7
- 239000002994 raw material Substances 0.000 description 6
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- 230000002159 abnormal effect Effects 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
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- 239000003054 catalyst Substances 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
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- 125000000524 functional group Chemical group 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
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- 238000000593 microemulsion method Methods 0.000 description 2
- 239000012716 precipitator Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
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- 229910006587 β-Al2O3 Inorganic materials 0.000 description 2
- 229910003158 γ-Al2O3 Inorganic materials 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
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- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
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- 229920001223 polyethylene glycol Polymers 0.000 description 1
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- 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
- C01F7/32—Thermal decomposition of sulfates including complex sulfates, e.g. alums
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C01P2004/30—Particle morphology extending in three dimensions
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Abstract
The invention discloses a method for preparing self-assembled hollow alumina microspheres by using sesbania gum as a template, which comprises the following steps: adding aluminum sulfate octadecahydrate, dicyanodiamide and methyl pyrrolidone into deionized water, and performing ultrasonic dispersion to obtain a clear solution A; step two: gradually dropwise adding a sesbania gum solution into the solution A, adjusting the pH value to 8.2-9.2, and magnetically stirring to obtain a solution B; step three: transferring the solution B to a rotary micro-polymerization reactor for micro-polymerization reaction, and collecting a product to obtain a solid C; step four: washing the solid C for multiple times, and performing vacuum freeze drying to collect a white powdery solid D; step five: mixing the solid D with aluminum potassium fluoride, transferring the mixture into a muffle furnace for heat preservation, cooling, washing and drying to obtain self-assembled hollow alumina microspheres; the micro-nano spherical space structure naturally formed in sesbania gum is used as a growth template of the alumina seed crystal, and the obtained alumina has good grain orientation, uniform grains, lower production and manufacturing cost and simple production process.
Description
Technical Field
The invention belongs to the field of materials, and particularly relates to a method for preparing self-assembled hollow alumina microspheres by using sesbania gum as a template.
Background
Since the 30 s of the 20 th century, alumina raw materials gradually become important experimental raw materials due to low price and good mechanical properties, and the alumina raw materials are highly brilliant in the fields of buildings and engineering mechanical elements. The alumina is mainly divided into three types according to different crystal forms: alpha-Al2O3、β-Al2O3And gamma-Al2O3Wherein alpha-Al2O3Are stable, the strength of the particles is high, and are generally used in structural parts of aircraft, while beta-Al2O3And gamma-Al2O3The catalyst has wide application in the fields of catalyst carriers and photoelectrocatalysis due to the special appearance. Chemical precipitation process of preparing nano alpha-Al2O3Study of powder [ J]Chemical engineering techniques and developments, 2019,46(12):36-40.]
With the progress of times and the expansion of material application fields, higher requirements are also put forward on the fineness and purity of the alumina raw material and the preparation process in actual production, the micro-nano alumina is beneficial to improving the mechanical property of structural parts, the preparation process is simple and easy to implement, and the production cost is indirectly reduced. However, because the strength of the alumina is high, the micro-nano-scale alumina is also easy to generate an uncontrollable agglomeration phenomenon, so that how to explore a good way to prepare the micro-nano-scale alumina with a specific structure becomes a key work of research in the field. [ A.Arellano, J.lemus-Ruiz, D.Bouvard, L.Olms.Behavior of the Nano aluminum Powder formed by Slip Casting under Microwave Sintering [ J ] Materials Science form, 2018,3194 ]
In order to prepare micro-nano-scale alumina with controllable appearance, scientific researchers gradually explore production methods such as a micro-emulsion method and a sol-gel method for decades, but the production methods mostly adopt toxic and harmful organic reagents as templates, the growth specificity of the prepared alumina is limited, the preparation of the alumina with a specific structure is difficult to realize, and the further large-scale popularization is difficult to realize in the actual production life. Therefore, how to improve the preparation process and select a proper template agent becomes the key for solving the problems. (R.Asokamani.Granulation of Nano aluminium Powder for Improved flow behaviour by Spray Drying [ J ]. Transactions of the Indian Institute of Metals,2017,65(5) ]
The method is combined with the current research hotspot problem, creatively provides a method for exploring a micro-nano alumina production technology with low cost and high practicability by adopting a biomass material sesbania gum as a structural template agent through a reasonable design process, and has great industrial production reference value.
Disclosure of Invention
In order to avoid the defects of the technology, the invention aims to provide the method for preparing the self-assembled hollow alumina microspheres by using the sesbania gum as the template, which has simple preparation method and low cost, and the obtained alumina has good grain orientation and uniform grains.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for preparing self-assembled hollow alumina microspheres by using sesbania gum as a template comprises the following steps:
the method comprises the following steps: sequentially adding 5.5-7.5 g of aluminum sulfate octadecahydrate, 5.0-7.0 g of dicyanodiamide and 6.2-7.5 g of methyl pyrrolidone into 60-80 ml of deionized water, and performing ultrasonic dispersion to obtain a clear solution A;
step two: gradually dripping 20-40 ml of sesbania gum solution with the concentration of 1.2-2.4 mol/L into the solution A, then dripping 0.6-1.5 mol/L ammonia water solution to the pH value of 8.2-9.2, and finally heating, fully and magnetically stirring to obtain a solution B;
step three: and (3) moving the solution B into a rotary micro-polymerization reactor, and setting the following two stages of reaction for 5-8 h according to the degree of separation: the pressure of the first stage is 20-40 Pa, the temperature is 60-100 ℃, the rotation rate is 40-100 r/min, and the micro-polymerization reaction time is 1-2 h; the pressure of the second stage is 30-50 Pa, the temperature is 160-200 ℃, the rotation rate is 80-120 r/min, the micro-polymerization reaction time is 4-6 h, and a product is collected after the reaction is finished to obtain a solid C;
step four: washing the solid C with a dilute hydrochloric acid solution and ethanol for multiple times in sequence until the pH value is 6.2-7.2, and then carrying out vacuum freeze drying on the solid C to collect a white powdery solid D;
step five: solid D according to mass ratio: potassium aluminum fluoride (1-2): (2-3) uniformly mixing the two substances, moving the mixture into a muffle furnace, heating the mixture from room temperature to 400-600 ℃ at a heating rate of 6-10 ℃/min, keeping the temperature for 0.5-1 h, heating the mixture to 1100-1300 ℃ at a heating rate of 8-10 ℃/min, keeping the temperature for 0.5-2 h, naturally cooling the mixture to room temperature, collecting a product, washing the product with water and ethanol for multiple times, and drying the product to obtain the self-assembled hollow alumina microspheres.
Further, in the step one, ultrasonic dispersion is carried out for 15-25 min at the temperature of 60-80 ℃ to obtain a clear solution A.
Further, in the second step, the solution B is obtained by heating and magnetically stirring at a stirring speed of 400-500 r/min at 160-180 ℃ for 15-25 min.
Further, in the fourth step, the solid C is sequentially washed for 3 times by using a dilute hydrochloric acid solution with the concentration of 0.5-1.5 mol/L and ethanol until the pH value is 6.2-7.2.
Further, in the freeze drying process in the fourth step, the washed product C is placed in a vacuum freeze dryer to react for 8-12 hours in two stages: the temperature of the first stage is-50 to-20 ℃, and the freezing time is 2 to 4 hours; the vacuum degree of the second stage is-20 to-10 Pa, the drying time is 6 to 8 hours, and finally white powdery solid D can be obtained by collection.
And further washing the product collected in the fifth step with water and ethanol for 3 times respectively, and finally transferring the product into an infrared oven and drying the product for 28-32 hours at 80-100 ℃ to obtain the self-assembled hollow alumina microspheres.
The invention prepared by the process method has the following beneficial effects:
the invention uses the sesbania gum which is a biomass raw material with wide natural reserves as a template, and uses a micro-nano spherical space structure naturally formed in the sesbania gum as a growth template of the alumina seed crystal. Compared with the chemical template agents such as polyethylene glycol and the like which are commonly used at present, the sesbania gum template agent has the advantages of easily available raw materials, green and environment-friendly product, lower production and manufacturing cost, simple production process, capability of perfectly conforming to the national policy requirements on energy conservation and environmental protection, and potential for realizing large-scale production.
In addition, the existing micro-nano-scale alumina preparation technology is mainly completed by a one-step precipitation method such as a microemulsion method, a hydrothermal method and the like, and alumina seed crystals have the defects of low yield, poor growth orientation and the like. The invention creates a double-substance coprecipitation system, introduces dicyandiamide and ammonia water as double precipitants, effectively avoids the problems that the single precipitants are insensitive to product separation and have lower precipitation efficiency in solution reaction, effectively improves the preparation efficiency of the products, reduces the occurrence of side reactions in the system, improves the stability of the preparation technology and the purity of the products, and has better popularization value and application prospect technically.
The invention also has the following five beneficial effects:
the dissolving of an inorganic precursor reagent and two precipitants in the same system is successfully realized under the condition of skillfully controlling a heating centrifugal stirring process by selecting dicyandiamide and ammonia water as precipitants and introducing methyl pyrrolidone as a surfactant. Compared with a single precipitant, the two precipitants are introduced to effectively improve the precipitation efficiency of the product alumina seed crystal, improve the precipitation width of the reaction and the purity of the precipitated alumina seed crystal, and the improvement of the solution reaction efficiency is also beneficial to the uniform precipitation of the micro-nano alumina seed crystal.
The dicyandiamide and the methyl pyrrolidone introduced in the step (II) contain various heterogeneous functional groups such as hydroxyl, carbonyl and the like, and the various functional groups can be subjected to a bonding reaction with weak alkaline sesbania gum in an internal free chemical bond, so that abundant attachment points are provided for the double precipitator in a micro-nano structure in the sesbania gum, the double precipitator is ensured to successfully enter the template agent, and alumina seed crystals with specific orientation are separated, separated and grown at specific spatial points, the incidence rate of non-template precipitation reaction in the solution is reduced, and the yield of the self-assembled hollow alumina seed crystals is improved.
And (III) a two-in-one rotary micro-polymerization reaction is constructed, the specific surface area of the reaction is improved by the unique micro-channel structure in the micro-polymerization reactor, the effective collision of reaction particles and the uniform dispersion of products in the thermal motion process are promoted by synchronous rotation, the reaction efficiency is improved while the process operation steps are simplified, and the target product loss possibly existing in the multi-step reaction process is reduced. Meanwhile, the temperature control and pressurization steps in the first stage of the two-in-one rotary micro polymerization reaction effectively ensure the dissolving amount of sesbania gum in the reaction solution, provide a material basis for uniform precipitation and directional growth of alumina seed crystals attached to a template in the second stage main reaction, and ensure the yield of the self-assembled hollow alumina microsphere seed crystals.
And (IV) designing a 'two-step' vacuum freeze-drying process, wherein the 'two-step' vacuum freeze-drying process can remove liquid water in the system in a sublimed form after solidifying compared with the conventional process in which the drying is carried out in an oven. And compared with liquid water, the solid water has smaller internal hydrogen bond acting force, thereby reducing the uncontrollable agglomeration of the micro-nano self-assembled hollow alumina microspheres due to the strong interaction force of the hydrogen bonds, improving the dispersibility of the alumina seed crystals, avoiding subsequent physical methods such as ultrasonic dispersion and the like to disperse the alumina seed crystals, effectively shortening the preparation process, saving the preparation cost and improving the production efficiency.
And (V) introducing aluminum potassium fluoride powder in the 'two-step' vacuum sintering reaction to provide guidance for the oriented growth of alumina seed crystals, efficiently promoting the crystal form transformation process of alumina and the generation of self-assembled hollow alumina microspheres under the combined action of a template agent, ammonia gas and fluoride, improving the reaction efficiency and avoiding abnormal growth of crystal grains caused by long-time high-temperature solid-phase reaction.
Drawings
Fig. 1 is a scanning electron microscope test chart of the self-assembled hollow alumina microspheres prepared in example 2 of the present invention.
FIG. 2 is an X-ray diffraction pattern of self-assembled hollow alumina microspheres prepared in example 2 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following examples, which are not intended to limit the invention thereto.
Example 1:
the method comprises the following steps: sequentially adding 5.5g of aluminum sulfate octadecahydrate, 6.0g of dicyanodiamide and 7.5g of methyl pyrrolidone into 70ml of deionized water, and performing ultrasonic dispersion at 80 ℃ for 25min to obtain a clear solution A;
step two: gradually dropwise adding 40ml of 1.2mol/L sesbania gum solution into the solution A, then dropwise adding 1.0mol/L ammonia water solution until the pH value is 8.5, and finally heating at 160 ℃ at a stirring speed of 500r/min and magnetically stirring for 25min to obtain a solution B;
step three: the solution B was transferred to a rotary micropolymerization reactor and the following split was set up in two stages for reaction for 8 h: the pressure of the first stage is 40Pa, the temperature is 100 ℃, the rotation rate is 40r/min, and the micro-polymerization reaction time is 2 h; the pressure of the second stage is 30Pa, the temperature is 180 ℃, the rotation rate is 100r/min, the micro-polymerization reaction time is 6h, and a product is collected after the reaction is finished to obtain a solid C;
step four: washing the solid C with 1.5mol/L dilute hydrochloric acid solution and ethanol for 3 times respectively to reach the pH value of 6.5, and then placing the solid C in a vacuum freeze dryer to react for 12h in two stages: the temperature of the first stage is-50 ℃, and the freezing time is 2 h; the vacuum degree of the second stage is-20 Pa, the drying time is 6h, and finally white powdery solid D can be obtained by collection;
step five: solid D according to mass ratio: potassium aluminum fluoride ═ 1: 3, uniformly mixing the two substances, transferring the mixture into a muffle furnace, heating the mixture from room temperature to 400 ℃ at the heating rate of 10 ℃/min, keeping the temperature for 1h, then heating the mixture to 1100 ℃ at the heating rate of 10 ℃/min, keeping the temperature for 2h, naturally cooling the mixture to room temperature, collecting the product, washing the product with water and ethanol for 3 times respectively in sequence, and finally transferring the product into an infrared oven and drying the product at 80 ℃ for 32h to obtain the self-assembled hollow alumina microspheres.
Example 2:
the method comprises the following steps: sequentially adding 7.5g of aluminum sulfate octadecahydrate, 5.0g of dicyanodiamide and 7.0g of methyl pyrrolidone into 60ml of deionized water, and performing ultrasonic dispersion at 70 ℃ for 15min to obtain a clear solution A;
step two: gradually dropwise adding 20ml of sesbania gum solution with the concentration of 2.4mol/L into the solution A, then dropwise adding ammonia water solution with the concentration of 1.5mol/L until the pH value is 8.2, and finally heating at the temperature of 170 ℃ at the stirring speed of 400r/min and magnetically stirring for 15min to obtain a solution B;
step three: the solution B was transferred to a rotary micropolymerization reactor and reacted for 5h in two stages with the following split: the pressure of the first stage is 30Pa, the temperature is 80 ℃, the rotation rate is 100r/min, and the micro-polymerization reaction time is 1 h; the pressure of the second stage is 40Pa, the temperature is 200 ℃, the rotation rate is 80r/min, the micro-polymerization reaction time is 5h, and a product is collected after the reaction is finished to obtain a solid C;
step four: washing the solid C with 1.0mol/L dilute hydrochloric acid solution and ethanol for 3 times respectively to reach the pH value of 7.2, and then placing the solid C in a vacuum freeze dryer to react for 10 hours in two stages: the temperature of the first stage is-30 ℃, and the freezing time is 4 h; the vacuum degree of the second stage is-10 Pa, the drying time is 8h, and finally white powdery solid D can be obtained by collection;
step five: solid D according to mass ratio: potassium aluminum fluoride ═ 1: 1, uniformly mixing the two substances, moving the mixture into a muffle furnace, heating the mixture from room temperature to 600 ℃ at the heating rate of 8 ℃/min, keeping the temperature for 0.5h, then heating the mixture to 1200 ℃ at the heating rate of 8 ℃/min, keeping the temperature for 0.5h, naturally cooling the mixture to room temperature, collecting a product, sequentially washing the product for 3 times by using water and ethanol, and finally moving the product into an infrared oven and drying the product for 28h at 100 ℃ to obtain the self-assembled hollow alumina microspheres.
FIG. 1 is a scanning electron microscope test chart of the self-assembled hollow alumina microspheres prepared in example 2. From fig. 1, it can be seen that the micron-sized alumina is uniformly dispersed, the aggregation among the particles is less, the particles are hollow microspheres in appearance, and the abnormal growth of alumina grains does not occur, indicating that example 1 successfully synthesizes the self-assembled hollow alumina microspheres by using sesbania gum as a template agent.
FIG. 2 is an X-ray diffraction pattern of self-assembled hollow alumina microspheres prepared in example 2. From fig. 2 it can be seen that the X-ray diffraction pattern of the substance has sharp peaks, indicating a higher purity and crystallinity of the substance. Next, the diffraction angles of 25.58 °, 35.16 °, 43.47 °, 52.55 °, 57.56 °, 66.76 ° and 68.42 ° corresponded to characteristic peak positions of alumina, and it was verified that the produced substance was alumina.
Example 3:
the method comprises the following steps: sequentially adding 6.5g of aluminum sulfate octadecahydrate, 7.0g of dicyanodiamide and 6.2g of methyl pyrrolidone into 80ml of deionized water, and performing ultrasonic dispersion at 60 ℃ for 22min to obtain a clear solution A;
step two: gradually dropwise adding 30ml of sesbania gum solution with the concentration of 2.0mol/L into the solution A, then dropwise adding 0.6mol/L ammonia water solution until the pH value is 9.2, and finally heating at the temperature of 180 ℃ at the stirring speed of 450r/min and magnetically stirring for 20min to obtain a solution B;
step three: the solution B was transferred to a rotary micropolymerization reactor and reacted for 7h in two stages with the following system: the pressure of the first stage is 20Pa, the temperature is 60 ℃, the rotation rate is 70r/min, and the micro-polymerization reaction time is 1.5 h; the pressure of the second stage is 50Pa, the temperature is 160 ℃, the rotation rate is 120r/min, the micro-polymerization reaction time is 4h, and a product is collected after the reaction is finished to obtain a solid C;
step four: washing the solid C with 0.5mol/L dilute hydrochloric acid solution and ethanol for 3 times respectively to reach the pH value of 6.2, and then placing the solid C in a vacuum freeze dryer to react for 8 hours in two stages: the temperature of the first stage is-20 ℃, and the freezing time is 3 h; the vacuum degree of the second stage is-15 Pa, the drying time is 7h, and finally white powdery solid D can be obtained by collection;
step five: solid D according to mass ratio: potassium aluminum fluoride ═ 1: 2, uniformly mixing the two substances, moving the mixture into a muffle furnace, heating the mixture from room temperature to 500 ℃ at the heating rate of 6 ℃/min, keeping the temperature for 0.8h, then heating the mixture to 1300 ℃ at the heating rate of 9 ℃/min, keeping the temperature for 1.5h, naturally cooling the mixture to room temperature, collecting a product, sequentially washing the product for 3 times by using water and ethanol, and finally moving the product into an infrared oven and drying the product for 30h at the temperature of 90 ℃ to obtain the self-assembled hollow alumina microspheres.
The self-assembled hollow alumina microsphere product prepared using the dual precipitant in example 3 was collected, weighed, and calculated to yield comparative data as shown in table 1 below:
table 1 comparison of yields of example 3 and blank samples
The blank sample mentioned in the above table is a self-assembled hollow alumina microsphere prepared by introducing only one precipitant, methyl pyrrolidone, according to the method of example 3. Compared with a single precipitant, the precipitation efficiency of the product alumina seed crystal can be effectively improved by introducing the two precipitants, the precipitation width and the yield of the target product are improved, and the technology has certain guiding significance and popularization value for actual production.
Example 4:
the method comprises the following steps: sequentially adding 6.5g of aluminum sulfate octadecahydrate, 7.0g of dicyanodiamide and 6.2g of methyl pyrrolidone into 80ml of deionized water, and performing ultrasonic dispersion at 60 ℃ for 25min to obtain a clear solution A;
step two: gradually dropwise adding 30ml of sesbania gum solution with the concentration of 2.0mol/L into the solution A, then dropwise adding 0.6mol/L ammonia water solution until the pH value is 9.2, and finally heating at the temperature of 180 ℃ at the stirring speed of 450r/min and magnetically stirring for 20min to obtain a solution B;
step three: the solution B was transferred to a rotary micropolymerization reactor and reacted for 7h in two stages with the following system: the pressure of the first stage is 50Pa, the temperature is 60 ℃, the rotation rate is 70r/min, and the micro-polymerization reaction time is 1.5 h; the pressure of the second stage is 50Pa, the temperature is 160 ℃, the rotation rate is 120r/min, the micro-polymerization reaction time is 4h, and a product is collected after the reaction is finished to obtain a solid C;
step four: washing the solid C with 0.8mol/L dilute hydrochloric acid solution and ethanol for 3 times respectively to reach the pH value of 6.2, and then placing the solid C in a vacuum freeze dryer to react for 9h in two stages: the temperature of the first stage is-20 ℃, and the freezing time is 4 h; the vacuum degree of the second stage is-15 Pa, the drying time is 7h, and finally white powdery solid D can be obtained by collection;
step five: solid D according to mass ratio: potassium aluminum fluoride ═ 1: 2.5 uniformly mixing the two substances, moving the mixture into a muffle furnace, heating the mixture from room temperature to 400 ℃ at the heating rate of 7 ℃/min, keeping the temperature for 0.8h, then heating the mixture to 1300 ℃ at the heating rate of 9 ℃/min, keeping the temperature for 1.5h, naturally cooling the mixture to room temperature, collecting the product, sequentially washing the product for 3 times by using water and ethanol, and finally moving the product into an infrared oven and drying the product at 95 ℃ for 31h to obtain the self-assembled hollow alumina microspheres.
The present invention is described in detail with reference to the above embodiments, and those skilled in the art will understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (6)
1. A method for preparing self-assembled hollow alumina microspheres by using sesbania gum as a template is characterized by comprising the following steps:
the method comprises the following steps: sequentially adding 5.5-7.5 g of aluminum sulfate octadecahydrate, 5.0-7.0 g of dicyanodiamide and 6.2-7.5 g of methyl pyrrolidone into 60-80 ml of deionized water, and performing ultrasonic dispersion to obtain a clear solution A;
step two: gradually dripping 20-40 ml of sesbania gum solution with the concentration of 1.2-2.4 mol/L into the solution A, then dripping 0.6-1.5 mol/L ammonia water solution to the pH value of 8.2-9.2, and finally heating, fully and magnetically stirring to obtain a solution B;
step three: and (3) moving the solution B into a rotary micro-polymerization reactor, and setting the following two stages of reaction for 5-8 h according to the degree of separation: the pressure of the first stage is 20-40 Pa, the temperature is 60-100 ℃, the rotation rate is 40-100 r/min, and the micro-polymerization reaction time is 1-2 h; the pressure of the second stage is 30-50 Pa, the temperature is 160-200 ℃, the rotation rate is 80-120 r/min, the micro-polymerization reaction time is 4-6 h, and a product is collected after the reaction is finished to obtain a solid C;
step four: washing the solid C with a dilute hydrochloric acid solution and ethanol for multiple times in sequence until the pH value is 6.2-7.2, and then carrying out vacuum freeze drying on the solid C to collect a white powdery solid D;
step five: solid D according to mass ratio: potassium aluminum fluoride (1-2): (2-3) uniformly mixing the two substances, moving the mixture into a muffle furnace, heating the mixture from room temperature to 400-600 ℃ at a heating rate of 6-10 ℃/min, keeping the temperature for 0.5-1 h, heating the mixture to 1100-1300 ℃ at a heating rate of 8-10 ℃/min, keeping the temperature for 0.5-2 h, naturally cooling the mixture to room temperature, collecting a product, washing the product with water and ethanol for multiple times, and drying the product to obtain the self-assembled hollow alumina microspheres.
2. The method for preparing the self-assembled hollow alumina microspheres by using the sesbania gum as the template as claimed in claim 1, wherein the method comprises the following steps: in the first step, the clear solution A is obtained by ultrasonic dispersion for 15-25 min at the temperature of 60-80 ℃.
3. The method for preparing the self-assembled hollow alumina microspheres by using the sesbania gum as the template as claimed in claim 1, wherein the method comprises the following steps: and in the second step, heating and magnetically stirring at the stirring speed of 400-500 r/min at the temperature of 160-180 ℃ for 15-25 min to obtain a solution B.
4. The method for preparing the self-assembled hollow alumina microspheres by using the sesbania gum as the template as claimed in claim 1, wherein the method comprises the following steps: and in the fourth step, the solid C is sequentially washed for 3 times by using a dilute hydrochloric acid solution with the concentration of 0.5-1.5 mol/L and ethanol respectively until the pH value is 6.2-7.2.
5. The method for preparing the self-assembled hollow alumina microspheres by using the sesbania gum as the template as claimed in claim 1, wherein the method comprises the following steps: in the step four, during the freeze drying process, the washed product C is placed in a vacuum freeze dryer to react for 8-12 hours in two stages: the temperature of the first stage is-50 to-20 ℃, and the freezing time is 2 to 4 hours; the vacuum degree of the second stage is-20 to-10 Pa, the drying time is 6 to 8 hours, and finally white powdery solid D can be obtained by collection.
6. The method for preparing the self-assembled hollow alumina microspheres by using the sesbania gum as the template as claimed in claim 1, wherein the method comprises the following steps: and D, washing the product collected in the step five by water and ethanol for 3 times respectively, and finally, transferring the product into an infrared oven and drying the product for 28-32 hours at the temperature of 80-100 ℃ to obtain the self-assembled hollow alumina microspheres.
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