阅读说明：本技术 一种α相氧化铝纳米粉的制备方法 (Preparation method of alpha-phase aluminum oxide nano powder ) 是由 董岩 刘睿 邵润 蒋建清 于 2020-06-28 设计创作，主要内容包括：本发明公开了一种α相氧化铝纳米粉的制备方法。首先配制铝盐和硫酸钾的混合溶液,调节pH得到氢氧化铝水合物的胶状沉淀,再用有机溶剂清洗沉淀物,烘干后在1000℃至硫酸钾熔点之间煅烧,水洗去除硫酸钾,干燥后可得到粒径仅4-5nm的α相纳米氧化铝粉,颗粒大小均匀且分散性良好。(The invention discloses a preparation method of alpha-phase alumina nano powder. Firstly, preparing a mixed solution of aluminum salt and potassium sulfate, adjusting the pH value to obtain colloidal precipitate of aluminum hydroxide hydrate, then cleaning the precipitate with an organic solvent, drying, calcining at the temperature of 1000 ℃ to the melting point of the potassium sulfate, washing with water to remove the potassium sulfate, and drying to obtain the alpha-phase nano alumina powder with the particle size of only 4-5nm, wherein the particle size is uniform and the dispersibility is good.)

1. A preparation method of alpha-phase alumina nano powder is characterized by comprising the following steps: the method comprises the following steps:

(1) preparing an aqueous solution of aluminum salt;

(2) adding potassium sulfate into the aluminum salt aqueous solution and dissolving to obtain a mixed aqueous solution of aluminum salt and potassium sulfate;

(3) adjusting the pH value of the mixed aqueous solution to 4-7 by using ammonia water to obtain a semitransparent gelatinous precipitate;

(4) washing the semi-transparent colloidal precipitate with organic solvent, and drying;

(5) calcining the obtained dried product at the temperature of more than 1000 ℃ and below the melting point of potassium sulfate for more than 1 hour;

(6) and washing and drying the obtained calcined product to obtain the alpha-phase aluminum oxide nano powder.

2. The method for preparing α -phase alumina nano-powder according to claim 1, characterized in that: the aluminum salt is aluminum nitrate, aluminum chloride, aluminum sulfate, aluminum potassium sulfate or aluminum ammonium sulfate.

3. The method for preparing α -phase alumina nano-powder according to claim 1, characterized in that: the mass fraction of the aluminum salt in the aluminum salt aqueous solution is between 0.1 and 20 percent.

4. The method for preparing α -phase alumina nano-powder according to claim 1, characterized in that: the mass fraction of the potassium sulfate in the mixed aqueous solution is not less than 5%.

5. The method for preparing α -phase alumina nano-powder according to claim 1, characterized in that: the organic solvent is methanol, ethanol, acetone or dimethylformamide.

Technical Field

The invention relates to a preparation method of alumina, in particular to a preparation method of alpha-phase alumina nano powder.

Background

Alumina powder has high hardness, heat resistance and corrosion resistance, is widely applied to products such as various plastics, rubber, ceramics, electronics, refractory materials and the like, and is one of the most important industrial raw materials. The alpha-phase alumina has high melting point, excellent heat conductivity, excellent corrosion resistance and wear resistance, and is most widely applied to all alumina crystal forms.

When the particle size is reduced to be less than 100nm, due to the surface effect, the quantum size effect, the volume effect and the macroscopic quantum tunneling effect of the nano-particle material, the nano-alumina shows good properties in thermal, optical, electrical, magnetic and chemical aspects, and has great application prospects in high-tech fields such as new materials, microelectronics, aerospace industry and the like and traditional industries. For example, the alumina ceramics fired by the high-dispersion nano alpha-phase alumina has excellent compactness, smoothness, cold and hot fatigue property, fracture toughness and creep resistance; the wear resistance of the product can be greatly improved by uniformly doping the high polymer material; the nano alpha-phase alumina can also be used as a far infrared emission material and a thermal insulation material with excellent performance to be applied to textile products; the high-dispersion nano alpha-phase alumina is also used for preparing high-transparency YAG laser crystals, electric insulating materials and the like.

However, highly dispersed nano alpha phase alumina is difficult to prepare because the preparation temperature must be above 1000 ℃ to convert alumina into alpha phase, and the nano particles are easily sintered at such high temperature. The existing preparation methods of nano alumina, such as a thermal decomposition method, a chemical precipitation method, a sol-gel method, a spray pyrolysis method, a solvothermal method, a freeze-drying method and the like, can not avoid contact mass transfer of alumina nano particles at a high temperature of 1000 ℃, and can not inhibit sintering growth of the nano particles, so that dispersed alpha alumina nano particles are difficult to obtain. So far, there is no method for efficiently preparing highly dispersed alpha phase alumina particles of 100nm or less, and it is more difficult to prepare ultra-small particle size highly dispersed alpha phase alumina particles of 10nm or less. In the prior art, agglomeration and sintering among nano aluminum oxide particles in the high-temperature calcination process cannot be avoided, and the prepared nano alpha-phase aluminum oxide is also the agglomerate of nano particles. In order to realize the efficient preparation of the alpha-phase alumina nano powder with high dispersion of 100nm or even below 10nm, the problem needs to be effectively solved.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a preparation method of alpha-phase alumina nano powder with ultra-small particle size and high dispersion.

The technical scheme is as follows: the invention provides a preparation method of alpha-phase alumina nano powder, which comprises the following steps:

(1) preparing an aqueous solution of aluminum salt;

(2) adding potassium sulfate into the aluminum salt aqueous solution and dissolving to obtain a mixed aqueous solution of aluminum salt and potassium sulfate;

(3) adjusting the pH value of the mixed aqueous solution to 4-7 by using ammonia water to obtain a semitransparent gelatinous precipitate;

(4) washing the semi-transparent colloidal precipitate with organic solvent, and drying;

(5) calcining the obtained dried product at the temperature of more than 1000 ℃ and below the melting point of potassium sulfate for more than 1 hour;

(6) and washing and drying the obtained calcined product to obtain the alpha-phase aluminum oxide nano powder.

Further, the aluminum salt is aluminum nitrate, aluminum chloride, aluminum sulfate, aluminum potassium sulfate or aluminum ammonium sulfate.

Furthermore, the mass fraction of the aluminum salt in the aluminum salt aqueous solution is between 0.1% and 20%.

Further, the mass fraction of potassium sulfate in the mixed aqueous solution is not less than 5%, and less than 5% cannot effectively isolate hydrated aluminum hydroxide nanoparticles.

Further, the organic solvent is methanol, ethanol, acetone or dimethylformamide.

Agglomeration and sintering are difficult technical bottlenecks to overcome in the nanoparticle preparation process. This is because nanoparticles have small particle size and large surface energy, are in an energy unstable state, and are very likely to agglomerate under the action of van der waals forces, inter-particle electrostatic forces, and the like. Under the action of surface hydrogen bonds, chemical bonds and the like, the nanoparticles can be subjected to unrecoverable hard agglomeration. The problem of particle agglomeration is further exacerbated by the action of capillary surface tension and liquid phase bridges that the nanoparticles undergo during drying. At high temperatures, however, nanoparticles are highly susceptible to sintering, resulting in particles that adhere and coalesce rapidly into long lengths. For these reasons, it is extremely difficult to prepare dispersed nanoparticles at high temperatures.

The present invention first prepares mixed water solution containing aluminum salt and potassium sulfate, and adjusts pH value to generate colloidal precipitate. The colloidal precipitate consists of a spatial network of ultra-small nanoparticles of hydrated aluminum hydroxide and a large amount of water contained in the spatial network, in which potassium sulfate is dissolved. When the colloidal precipitate is washed with an organic solvent such as ethanol, the solubility of potassium sulfate in water is reduced and the precipitated potassium sulfate separates out the hydrated aluminum hydroxide nanoparticles. When the calcination is continued above the alpha phase transition temperature and below the potassium sulfate melting point (1069 ℃), the hydrated aluminum hydroxide nanoparticles are converted into alpha-phase aluminum oxide, and simultaneously, due to the isolation effect of the solid potassium sulfate, agglomeration and sintering growth cannot occur among the nano aluminum oxide particles. And washing and drying the product after high-temperature calcination to obtain the highly-dispersed alpha alumina nano particles with ultra-small particle size, wherein the size of the nano particles is only 4-5 nm.

Has the advantages that: the alpha-phase alumina nano powder has high dispersity and ultra-small grain diameter which is as small as 4-5 nm. And the raw materials are low in price, and the process is simple and easy to implement, so that the method has obvious superiority.

Drawings

FIG. 1 shows alpha alumina nanoparticles prepared at 1050 ℃ using the method of the present invention, having a particle size of about 4-5nm and good dispersibility.

Detailed Description