CN101279754A - Preparation method of nano-boehmite with various shapes - Google Patents

Abstract

The invention relates to a method for preparing nano-boehmite with various shapes, in particular to a method for preparing nano-boehmite materials such as nanofibers, core shell inner spheres, solid spheres, and hollow spheres, belonging to the preparation of inorganic nanomaterials technology field. The method of the present invention is characterized in that: a certain amount of soluble aluminum salt is dissolved in water, and an organic auxiliary solvent is added, and a certain amount of shape control agent is added under stirring, and then the mixed solution is placed in a hydrothermal kettle, and the React at a temperature of 160-250°C for 2-60 hours. After the reaction, the product is separated, and the obtained precipitate is washed with deionized water and ethanol several times, and finally dried at 60-80°C to obtain Boehm with a specific shape. stone material. The morphology control agent is any one of citrate, tartrate, oxalate and disodium edetate, and its addition amount is 0-20 mmol.

Description

Preparation method of nano-boehmite with various shapes

technical field

The invention relates to a preparation method of nano-boehmite with various shapes, in particular to a preparation method of nano-boehmite materials such as nanofibers, core-shell spheres, solid spheres, hollow spheres, etc., belonging to inorganic nanomaterials Preparation technology field.

Background technique

Alumina fiber has the advantages of high strength, large modulus, small thermal conductivity, low thermal expansion coefficient, good heat and high temperature resistance, and high surface activity. It can form composite materials with superior performance with resin, metal, and ceramics, and is widely used In aerospace, military and other high-tech fields.

The alumina core-shell structure and the hollow part of the hollow sphere can accommodate a large number of guest molecules or large-size guests, resulting in some exotic properties based on microscopic "encapsulation" and "wrapping" effects. These nanoscale or mesoscale hollow structures Compared with its bulk materials, it has attracted great attention due to its low density, high specific surface area, good stability, good surface permeability and special optical properties, and the hollow shell can be formed according to people's interests. Constructed of various valuable materials. Due to the many characteristics above, it has many important applications in the fields of chemistry, biology and material science, such as filtration, coating, pigments, artificial cells, catalysts, protection of photosensitive substances, cosmetics, inks, fuels, separation Materials, coatings, controlled release capsules, drug delivery, electrical devices, and acoustic insulation.

The above nano-alumina with special application due to its special shape can be obtained by calcining aluminum hydroxide or boehmite at high temperature.

At present, among many preparation methods of boehmite and alumina materials, gas phase method, sol-gel method, microemulsion method, precipitation hydrolysis method and so on occupy a more important position. For example: "Advanced Materials" (Advanced Materials, 2007, 19, 102) uses atomic deposition to prepare hollow spheres; East China Institute of Technology Li et al. (Ind. Eng. Chem. Res. 2007, 46, 8004) uses high-speed flame spraying A hollow sphere with a shell thickness of about 30nm was produced; Pan et al. (Ceramics International, 2007, 33, 305) from the Shanghai Institute of Ceramics, Chinese Academy of Sciences prepared Al/AlOOH core-shell nanoparticles by reacting aluminum foil with sulfuric acid; Claus Feldmann et al. (Nano letter, 2007, 7, 3489) prepared AlOOH hollow spheres with a diameter of about 30nm by microemulsion method; but these methods either require high temperature, expensive and complicated equipment, or use a lot of organic solvents, and the operating conditions are generally relatively harsh. Therefore, it is of great significance to develop a nano-boehmite synthesis method with easy-to-obtain raw materials, low cost, simple operation, convenient handling, mild reaction conditions and easy industrialization.

Contents of the invention

The purpose of the present invention is to provide a method for preparing nano-boehmite with various shapes, so as to overcome the defects in the prior art.

The alumina, aluminum hydroxide and hydrates thereof prepared in the present invention are similar to the natural mineral boehmite in structure, so they are called boehmite materials.

A method for preparing nano-boehmite with multiple shapes of the present invention is characterized in that it has the following processes and steps:

a. Dissolving a certain amount of soluble aluminum salt in a certain amount of water to form a solution with a concentration of 0.01-0.2mol/L;

b. Under stirring, add 0-30ml of organic auxiliary solvent and mix well;

c. Add a certain amount of morphology control agent to the above solution under stirring at room temperature, and continue stirring to form a uniform solution;

d. Transfer the above mixed solution to a hydrothermal kettle, tighten the lid of the kettle, place it in an oven, and react at a temperature of 160-250°C for 2-60 hours. After the reaction, centrifuge and separate the precipitate with deionized water and dry Wash several times with water and ethanol;

e. Dry the clean precipitate obtained above at 60-80°C for 12 hours to obtain boehmite with a specific shape;

Described soluble aluminum salt is any one in aluminum nitrate, aluminum chloride, aluminum sulfate;

Described organic auxiliary solution is any one in methanol, ethanol, acetone, carbon tetrachloride, ethylene glycol;

The shape control agent is any one of citrate, tartrate, oxalate, disodium edetate and sodium alginate; the added amount of the shape control agent is 0-2 mmol.

In the preparation method of the present invention, the mechanism of using a shape control agent to form nano-boehmite with various shapes is as follows:

Citrate, tartrate, disodium ethylenediaminetetraacetate (EDTA-2Na) are good complexing agents for many metal ions such as Ca ²⁺ , Zn ²⁺ , Al ^{3+ ,} etc., and can form composite ions, while It also acts as a stabilizer for morphology control agents, forming complex microstructures. Self-assembly is considered to be an effective means to form composite ultrastructures. Self-assembly is generally driven by van der Waals forces and hydrogen bonds.

Take citrate as an example: when trisodium citrate is added: under high temperature and high pressure, Al(NO ₃ ) ₃ ·9H ₂ O reacts with deionized water to form a boehmite phase. In the early stage of the reaction, Al(NO ₃ ) ₃ 9H ₂ O was slowly hydrolyzed to generate boehmite nanoparticles, and then citrate ions selectively adsorbed on the surface of boehmite nanoparticles, allowing the boehmite nanoparticles to grow in one direction form nanorods. The hydroxyl groups in the citrate ions form hydrogen bonds with the hydroxyl groups in the octahedral structure AlO ₆ in the boehmite, and through the strong interaction of the hydrogen bonds, self-assemble into an ordered nanorod bundle structure. As for the formation of the core-shell structure and even the hollow sphere, it is due to the dissolution of the core of the sphere with the prolongation of the reaction time at high temperature.

Citrate is a good complexing agent for many metal ions, capable of forming complex ions, and it can also be used as a morphology control agent and stabilizer. Citrate and Al ³⁺ form coordination ions, the structure of which is formed as follows:

The reaction equation is:

Al ³⁺ +citrate ^3- →Al(citrate)

Al ³⁺ +H ⁺ +citrate ^3- →AlH(citrate) ⁺ (1)

Al ³⁺ 3H ₂ O→Al(OH) ₃ (amorphous)+3H ⁺ (2)

Al(OH) ₃ →r-AlOOH+H ₂ O (3)

Citrate ^3- in the above formula represents citrate ion.

The characteristics of the inventive method

The inventive method has following characteristics:

(1) The selected system of the inventive method can synthesize boehmite with different morphology structures by adjusting the amount, reaction temperature and time of the morphology control agent in the same system, thus greatly reducing the production cost and improving the production efficiency. Production efficiency of nanomaterials.

(2) The method of the present invention adopts a hydrothermal method, and the product has many shapes with good reproducibility, which lays a good foundation for the research and development of functional materials.

(3) The water and organic solvent used in the method of the present invention can be recycled and reused, so it has the advantages of easy operation, simple process equipment and no pollution.

Description of drawings

Fig. 1 is a topography image obtained by a transmission electron microscope (TEM) of the product of Example 1 of the present invention.

Fig. 2 is a structure diagram obtained by X-ray powder diffraction (XRD) of the product of Example 1 of the present invention.

Fig. 3 is a topography image obtained by a transmission electron microscope (TEM) of the product of Example 2 of the present invention.

Fig. 4 is a topography image obtained by a transmission electron microscope (TEM) of the product of Example 3 of the present invention.

Fig. 5 is a topography image obtained by a transmission electron microscope (TEM) of the product of Example 4 of the present invention.

Fig. 6 is a topography image obtained by a transmission electron microscope (TEM) of the product of Example 5 of the present invention.

Fig. 7 is a topography image obtained by a transmission electron microscope (TEM) of the product of Example 6 of the present invention.

Fig. 8 is a topography image obtained by a transmission electron microscope (TEM) of the product of Example 7 of the present invention.

Detailed ways

The following are examples of experiments and results of boehmite nanofibers, solid spheres, core-shell structures, and hollow spheres prepared by the method of the present invention.

Embodiment one: concrete steps are as follows:

a. Dissolve 3mmol aluminum nitrate in 20ml deionized water to form a uniformly mixed solution;

b. Under stirring, add 20ml of absolute ethanol and mix well;

c. Under stirring at room temperature, add 1 mmol of sodium citrate to the above solution, and continue stirring for 50 minutes to form a uniformly mixed solution;

d. Transfer the uniformly mixed solution to a hydrothermal kettle, tighten the lid of the kettle, and place it in an oven at 220° C. for 48 hours. After the reaction, centrifuge and wash several times with deionized water and absolute ethanol.

e. Dry the sample obtained in step d at 80° C. for 12 hours to obtain boehmite with a core-shell structure, that is, a sphere-within-sphere structure.

The product obtained in this example was characterized by a transmission electron microscope (TEM) on the morphology of the product. It can be seen from Figure 1 that the obtained product has a core-shell structure with an outer sphere diameter of about 1.7 μm and an inner sphere diameter of 1 μm, and the outer shell layer is composed of nanofiber bundles. As can be seen from Figure 2, the XRD results show that the product is pure AlOOH (consistent with the 21-1307JCPDS card).

Embodiment two: concrete steps are as follows:

a. Dissolve 0.5mmol aluminum sulfate in 20ml deionized water to form a uniformly mixed solution;

b. Under stirring, add 20ml of absolute ethanol and mix well;

c. Under stirring at room temperature, add 0.5 mmol of sodium citrate to the above solution, and continue stirring for 30 minutes to form a uniformly mixed solution;

d. Transfer the uniformly mixed solution to a hydrothermal kettle, tighten the lid of the kettle, and place it in an oven at 180°C for 6-18 hours. After the reaction, centrifuge and wash several times with deionized water and absolute ethanol.

e. Dry the sample obtained in step d at 60° C. for 12 hours to obtain boehmite with a solid spherical structure.

The product obtained in this example was dispersed in absolute ethanol, and the morphology of the product was characterized by a transmission electron microscope (TEM). It can be clearly seen from Fig. 3 that there are boehmite solid spheres with a diameter of about 1 μm.

Embodiment three: concrete steps are as follows:

a. Dissolve 2mmol aluminum nitrate in 20ml deionized water to form a uniformly mixed solution;

b. Under stirring, add 20ml acetone and mix well;

c. Under stirring at room temperature, add 0.5 mmol of sodium citrate to the above solution, and continue stirring for 30 minutes to form a uniformly mixed solution;

d. Transfer the uniformly mixed solution to a hydrothermal kettle, tighten the lid of the kettle, and place it in an oven at 200°C for 24 hours. After the reaction, centrifuge and wash several times with deionized water and absolute ethanol.

e. Dry the sample obtained in step d at 60° C. for 12 hours to obtain boehmite with a core-shell structure.

The product obtained in this example is dispersed in absolute ethanol, and the morphology of the product is characterized by a transmission electron microscope (TEM). From Figure 4, it can be clearly seen that the obtained product is an outer sphere with a diameter of about 2 to 3 μm and an inner sphere with a diameter of It has a core-shell structure of 1 μm, and the outer shell layer is formed by dense nanocrystals.

Embodiment four: concrete steps are as follows:

a. Dissolve 1mmol aluminum chloride in 20ml deionized water to form a uniformly mixed solution;

b. Under stirring, add 20ml of ethylene glycol and mix well without adding shape control agent;

c. Transfer the uniformly mixed solution to a hydrothermal kettle, tighten the lid of the kettle, and place it in an oven at 200°C for 24 hours. After the reaction, centrifuge and wash several times with deionized water and absolute ethanol.

d. Dry the sample obtained in step d at 60° C. for 12 hours to obtain boehmite with a fiber bundle structure.

Disperse the product obtained in this example in absolute ethanol, and use a transmission electron microscope (TEM) to characterize the morphology of the product. From Figure 5, it can be clearly seen that the boehmite with a length of about 200nm and a diameter of about 5-10nm stone fiber.

Embodiment five: the specific steps are as follows:

a. Dissolve 2mmol aluminum nitrate in 10ml deionized water to form a uniformly mixed solution;

b. Under stirring, add 30ml of absolute ethanol and mix well;

c. Under stirring at room temperature, add 1.5 mmol of sodium citrate to the above solution, and continue stirring for 30 minutes to form a uniformly mixed solution;

d. Transfer the uniformly mixed solution to a hydrothermal kettle, tighten the lid of the kettle, and place it in an oven at 200°C for 6-18 hours. After the reaction, centrifuge and wash several times with deionized water and absolute ethanol.

e. Dry the sample obtained in step d at 60° C. for 12 hours to obtain boehmite with a hollow sphere structure.

The product obtained in this example was dispersed in absolute ethanol, and the morphology of the product was characterized by a transmission electron microscope (TEM). From Figure 6, it can be clearly seen that the boehmite hollow spheres with a diameter of about 0.5-1 μm.

Embodiment six: the specific steps are as follows:

a. Dissolve 2mmol aluminum chloride in 40ml deionized water;

b. Under stirring at room temperature, add 0.2 mmol of disodium ethylenediaminetetraacetic acid (EDTA-2Na) into the above solution, and continue stirring for 30 minutes to form a well-mixed solution;

c. Transfer the uniformly mixed solution to a hydrothermal kettle, tighten the lid of the kettle, and place it in an oven at 200°C for 12 hours. After the reaction, centrifuge and wash several times with deionized water and absolute ethanol.

d. Dry the sample obtained in step d at 60° C. for 12 hours to obtain boehmite with a fiber bundle structure.

The product obtained in this example was dispersed in absolute ethanol, and the morphology of the product was characterized by a transmission electron microscope (TEM). From Figure 7, it can be clearly seen that the boehmite with a length of about 500nm and a diameter of about 5-20nm Stone Nanorods.

Embodiment seven: the concrete steps are as follows:

a. Dissolve 2mmol aluminum nitrate in 40ml deionized water;

b. Under stirring at room temperature, add 0.5 mmol of sodium tartrate to the above solution, and continue stirring for 30 minutes to form a uniformly mixed solution;

c. Transfer the uniformly mixed solution to a hydrothermal kettle, tighten the lid of the kettle, and place it in an oven at 200°C for 24 hours. After the reaction, centrifuge and wash several times with deionized water and absolute ethanol.

d. Dry the sample obtained in step d at 60° C. for 12 hours to obtain boehmite with a fiber bundle structure.

Disperse the product obtained in this example in absolute ethanol, and use a transmission electron microscope (TEM) to characterize the morphology of the product. It can be clearly seen from Figure 8 that the length is about 200nm and the diameter is about 10-40nm. boehmite fiber bundles.

Claims (1)

1. the preparation method of one kind of multiple pattern nm boehmite is characterized in that having following process and step:

A. a certain amount of aluminum soluble salt is dissolved in a certain amount of water, forming concentration is the solution of 0.01～0.2mol/L;

B. under agitation, add organic secondary solvent of 0～30ml, and mix;

C. under stirring at room, a certain amount of morphology control agent is joined in the above-mentioned solution, continue to stir to form uniform solution;

D. above-mentioned mixed solution is transferred in the water heating kettle, screws kettle cover, place baking oven, under 160～250 ℃ of temperature, react 2～60h, after reaction finishes, centrifugation, throw out is used deionized water and absolute ethanol washing for several times;

E. the clean throw out with above-mentioned gained descended dry 12 hours at 60～80 ℃, promptly got the boehmite of specific morphology;

Described aluminum soluble salt is any in aluminum nitrate, aluminum chloride, the Tai-Ace S 150;

Described organic assisted solution is any in methyl alcohol, ethanol, acetone, tetracol phenixin, the ethylene glycol;

Described morphology control agent is any in Citrate trianion, tartrate, oxalate, disodium ethylene diamine tetraacetate, the sodium alginate; The add-on of morphology control agent is 0～2mmol.

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