CN1948155A - A kind of preparation method of monodisperse nano α-alumina particle powder - Google Patents

Abstract

The invention discloses a preparation method of monodisperse agglomeration-free alpha-alumina particle powder. Adding an auxiliary isolation phase of water-soluble salt into an aluminum salt solution, adding alpha-alumina seed crystal and a hydrophilic surfactant into the system, stirring to fully dissolve the hydrophilic surfactant, slowly dropping an alkali aqueous solution into a reaction liquid, homogenizing the reaction system after the reaction is finished, drying, grinding and mixing, and calcining the ground powder at 950-1100 ℃ to obtain the 10-30 nm monodisperse alpha-alumina nano-particle powder.

Description

A kind of preparation method of monodisperse nano α-alumina particle powder

technical field

The invention relates to a method for preparing monodisperse non-agglomerated nano-α-alumina particle powder used in the fields of ceramics, catalysts, electronics industry, coating materials, biomedicine and optical materials.

Background technique

Monodisperse and non-agglomerated nano-α-alumina particle powder is an indispensable raw material for preparing high-density, fine-grained nano-α-alumina ceramics. Due to the unique chemical stability and thermal, electrical and optical properties of nano-α-alumina, it has important application value in many fields. α-alumina is the most thermodynamically stable structure of alumina. It is generally produced by calcination at a high temperature above 1100°C by using aluminum hydroxide or transition phase alumina, but hard agglomeration will inevitably occur during high temperature calcination. At present, the preparation of α-alumina mostly uses processes such as chemical vapor deposition, liquid phase sol-gel method, chemical precipitation method and solid phase combustion decomposition method. Among them, chemical vapor deposition can precisely control the reaction conditions, and obtain nanopowders with different particle sizes and shapes and better dispersion under different operating conditions, but the cost is high, the yield is low, and it is difficult to realize industrial scale production. The sol-gel method can produce high-purity ultrafine powder, but the price of raw materials is high, the organic solvent is toxic and hard agglomeration will be formed during high temperature treatment. The solid-phase method is easy for industrial production, but the pyrolysis process is easy to cause hard agglomeration of the powder. The currently commonly used chemical precipitation preparation method has simple process, low cost and is suitable for industrial production, but there is a serious problem of hard agglomeration.

Chinese invention patent application 200310114455.8 discloses a method for preparing non-agglomerated nano-α-Al ₂ O ₃ powder, which is to fully disperse nano-carbon black in an inorganic aluminum salt solution with a concentration of 0.5-3.0 mol/L, and then In the turbulent reaction field, slowly add a certain concentration of lye, control the pH value of the final reaction solution at 5.0-8.0, sink for 7-12 hours after the reaction is completed, then filter and wash, and the filter cake is at 1000-1200 ℃ for 1 to 3 hours in an inert gas furnace, and then calcined in an air furnace at 600 to 800 ℃ until the surface coating is completely removed, and the α - Al ₂ O ₃ powder. Since this patent uses insoluble nano-carbon black as a dispersant, to ensure its effect, the requirements for the dispersion of carbon black in the reaction solution during the preparation process are particularly high. On the other hand, the preparation cost of this technology will also be higher.

Contents of the invention

The invention provides a method which can overcome the disadvantages of the prior art and obtain monodisperse nanometer α-alumina particle powder material with relatively low cost and relatively simple process.

The method of the present invention is to add the auxiliary isolation phase of water-soluble salt to the aluminum salt solution with a molar concentration of 0.005～0.1mol/l of aluminum ions, and the molar ratio of water-soluble salt to aluminum salt is 10≤m≤80, and the auxiliary isolation phase is made by stirring. Fully dissolve the isolation phase in the aluminum salt solution, then add a hydrophilic surfactant into the system at 0.5-1.0g/100ml (aluminum salt solution), stir to fully dissolve the hydrophilic surfactant, and then add it to the reaction liquid Slowly drop the aqueous alkali solution to make the final pH of the system 8.5-10. After the reaction is completed, homogenize the reaction system, then dry it, grind and mix the obtained powder, and grind and mix the powder Calcination is carried out at 950-1100° C. to obtain monodisperse and non-agglomerated α-alumina nanoparticle powder of 10-30 nm.

The concept of the method of the present invention is to avoid the formation of hard agglomerates when the alumina transforms from the transition phase to the α-Al ₂ O ₃ phase during the calcination process. The alumina nanoparticles are separated from each other by the auxiliary isolation phase of the active salt, thereby avoiding the problem of hard agglomeration caused by the thermal aggregation or the formation of sintering necks of the Al ₂ O ₃ nanoparticles during calcination, and ensuring the obtained α-Al ₂ O Agglomeration-free monodispersity of ₃ .

In the present invention, for example, α-Al ₂ O ₃ seed crystals whose amount is 1-3% of the amount of the aluminum salt is added to the reaction system after the auxiliary isolation dispersed phase is fully dissolved. The α-Al ₂ O ₃ seeds provide nucleation sites, lowering the transition barrier of transition state alumina to α-Al ₂ O ₃ , thereby lowering the formation temperature of α-Al ₂ O ₃ .

The optimal control range of the method of the present invention is: the molar concentration of aluminum ions in the reaction system is 0.01 to 0.05 mol/l, the molar ratio of the added water-soluble salt to aluminum salt is 20 to 60, and the amount of the added seed crystal substance It is 1.5-2.5% of the amount of inorganic aluminum salt, and the added surfactant can be a combination of PEG200 and PEG100 (polyethylene glycol, Polyethylene Glycol, HO(CH ₂ CH ₂ O) _n H) in any proportion formed mixture. The aluminum salt used in the present invention is preferably Al(NO ₃ ) ₃ , the added water-soluble salt is sodium chloride or potassium chloride, the alkali aqueous solution used is ammonia water, and the final pH value of the reaction system is 9.

Experiments show that the ratio of the amount of the auxiliary isolation phase adopted in the method of the present invention to the amount of alumina is a necessary condition, because the auxiliary isolation phase incorporated is too little to achieve a good isolation effect, so that monodispersion cannot be obtained. The α-alumina nanopowder; too much auxiliary isolation phase mixed in will cause serious two-phase separation at high temperature, and the phase separation will cause the coarsening of some nanoparticles, so that the particle size of the product will be uneven. In addition, if the aluminum ion concentration is too high in the present invention, high-concentration aluminum hydroxide particles are likely to collide and cause agglomeration during the precipitation process; but if the aluminum ion concentration is too small, it will be unfavorable for mass production. In the drying process, the auxiliary isolation phase is generally easier to precipitate, so that the two solid phases of the auxiliary isolation phase and the alumina precursor are not uniformly mixed, so after drying, it is necessary to grind and mix the auxiliary isolation phase and the alumina precursor to fully and uniformly mix.

The advantages of the present invention are:

(1) In the chemical precipitation process, due to the introduction of a chemically stable auxiliary isolation phase, and because the isolation phase is a water-soluble salt, it is easily dissolved in water, so that the prepared precursor-aluminum hydroxide particles can be assisted The separation phase is excellently separated, avoiding the contact of alumina nanoparticles generated during calcination, and inhibiting the agglomeration problem caused by the thermal aggregation or formation of sintering necks of Al ₂ O ₃ nanoparticles during calcination, thus ensuring the obtained Monodispersity _of α- _Al2O3 .

(2) and the degree of dispersion of the auxiliary separating phase used in the present invention in the reaction system is far better than that of the nano-carbon black powder adopted in the prior art in the reaction system, and the system is specially carried out when there is no need for reaction. decentralized processing.

(3) The whole process is simple, low in cost, non-polluting, has no special requirements on equipment, and can be produced on a large scale.

(4) The whole process is easy to adjust and control the conditions, and it is also easy to control the particle size, dispersion and phase of the product.

(5) The prepared nanoparticles are spherical, monodisperse, and have a narrow particle size distribution

Description of drawings

Accompanying drawing 1 is the X-ray diffraction spectrum of the embodiment final product prepared by the method of the present invention.

Accompanying drawing 2 is the selected area electron diffraction of the embodiment final product prepared by the method of the present invention.

Accompanying drawing 3 is the morphological figure of the transmission electron microscope of the final product of the example prepared by the method of the present invention.

Detailed ways

An embodiment of the invention is provided below:

1. Weigh 11.2539g of Al(NO ₃ ) ₃ 9H ₂ O and 70.128g of NaCl with a balance, and dissolve them in 300ml of deionized water. The molar concentration of aluminum ions in the solution is 0.01mol/l. NaCl and Al (NO ₃ ) The ratio of the amount of ₃ substances is 40, stirring constantly, after completely dissolving, filter to remove foreign impurities;

2. Add 0.0765g of α-Al ₂ O ₃ seed crystals to the above solution, stir with a magnetic stirrer for 30 minutes, and ultrasonically sonicate for 10 minutes, so that the α-Al ₂ O ₃ seed crystals are evenly dispersed in the mixed solution;

3. Add 0.75g of surfactants PEG200 and PEG1000 each, and continue stirring until PEG is completely dissolved;

4. Titrate the rapidly stirred mixed solution with concentrated ammonia water, the titration rate is about 2ml/min, the mixed solution becomes turbid to milky white, and the final pH value of the system is 9;

5. Homogenization system: magnetic stirring, aging;

6. Drying and grinding;

7. Calcined at 1000°C for 5h;

8. Centrifuge the calcined sample for 5 times with deionized water and 3 times with absolute ethanol, and check whether the auxiliary phase ions in the sample are cleaned with AgNO ₃ solution.

The X-ray diffraction spectrum of the sample obtained through the above treatment is shown in Fig. 1, and its diffraction spectrum is confirmed to be product α-Al ₂ O ₃ ; The selected area electron diffraction (SAED) of the sample obtained through the above treatment is shown in Fig. 2, showing that the product obtained is α - Al ₂ O ₃ single crystal; see Figure 3 for the TEM image of the sample obtained through the above treatment, which shows that the obtained α-Al ₂ O ₃ nanoparticles are 10nm monodisperse and non-agglomerated.

Claims (4)

1. A method for preparing monodisperse nanometer α-alumina particle powder. The aqueous solution of alkali is dropped into an aqueous solution of inorganic aluminum salt for reaction. After the reaction is completed, drying is carried out, and the obtained solid is calcined, and then the calcined Wash the treated solids to obtain monodisperse nano α-alumina, which is characterized in that the molar concentration of aluminum ions in the aluminum salt solution is 0.005-0.1mol/l, and an auxiliary isolation phase of water-soluble salt is added to the aluminum salt solution , the molar ratio of water-soluble salt to aluminum salt is 10≤m≤80, the auxiliary isolation phase is fully dissolved in the aluminum salt solution by stirring, and then the hydrophilic Active surfactant, stirring to fully dissolve the hydrophilic surfactant, and then slowly drop the aqueous alkali solution into the reaction liquid, so that the final pH of the system is 8.5-10, homogenize the reaction system, and carry out further Perform drying treatment, grind and mix the obtained powder, and calcinate the submerged powder at 950-1100° C. to obtain monodisperse α-alumina nanoparticles. 2. The method for preparing monodisperse nanometer α-alumina particle powder according to claim 1, characterized in that α-Al ₂ O ₃ seed crystals are added to the reaction system after the auxiliary isolation dispersed phase is fully dissolved. The amount of seed crystal added is 1-3% of the amount of aluminum salt substance. 3. The method for preparing monodisperse nanometer α-alumina particle powder according to claim 2, characterized in that the molar concentration of aluminum ions in the reaction system is 0.01 to 0.05 mol/l, and the added water-soluble salt and aluminum salt The molar ratio of the compound is 20-60, the added seed crystal amount is 1.5-2.5% of the molecular weight of the inorganic aluminum salt, and the added surfactant is a mixture of PEG200 and PEG1000 in any proportion. 4. The method for preparing monodisperse nanometer α-alumina particle powder according to claims 1 to 3, characterized in that the aluminum salt used is Al(NO ₃ ) ₃ , and the added water-soluble salt is sodium chloride Or potassium chloride, the aqueous alkali solution used is ammonia water, and the final pH value of the reaction system is 9.

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