CN114956140B

CN114956140B - Preparation method of spherical alumina powder

Info

Publication number: CN114956140B
Application number: CN202210568770.0A
Authority: CN
Inventors: 马淑云; 王世贤; 吕慧滨; 黄建林; 郝婷婷
Original assignee: Henan Tianma New Material Co ltd
Current assignee: Henan Tianma New Material Co ltd
Priority date: 2022-05-24
Filing date: 2022-05-24
Publication date: 2023-08-08
Anticipated expiration: 2042-05-24
Also published as: CN114956140A

Abstract

According to the preparation method of the spherical alumina powder, in the solvothermal reaction process, the shape, size, granularity distribution and dispersion effect of alumina can be effectively controlled by regulating the size and mass ratio of the aluminum salt to the polyol and the nano alumina seed crystal and the solvothermal reaction condition, the viscosity of the polyol is rapidly reduced under the high temperature of hydrothermal conditions, the precipitation reaction of the aluminum salt is promoted, the viscosity of the polyol is increased along with the reduction of the temperature after the reaction is complete, the agglomeration of reaction intermediate products is inhibited, meanwhile, the polyol can be repeatedly used through a subsequent distillation process, and the preparation cost can be greatly reduced.

Description

Preparation method of spherical alumina powder

Technical Field

The invention belongs to the technical field of inorganic oxide powder material preparation, and particularly relates to a preparation method of spherical alumina powder.

Background

As an inorganic oxide material widely used, the alumina has the mechanical properties of high melting point, high strength, high hardness and the like, and also has the properties of high resistivity, high dielectric constant, high oxidation resistance, high thermal conductivity and the like. The material is widely applied to the fields of ceramics, paint, catalysts, polishing or grinding tools and the like, and is also an important material of a lithium ion battery ceramic diaphragm at present. The performance indexes of the alumina powder, including particle size, particle size distribution, morphology characteristics and specific surface area, have great influence on the preparation process and performance indexes of the material. In order to realize stable control of the material preparation process and reliability of high-performance materials, research and development of the alumina powder preparation process are always focused on.

The preparation method of alumina is more, including gas phase method, liquid phase method, sol-gel method, metal aluminum hydrolysis method, water (solvent) heat, etc., and through the interference of external conditions, such as mechanical grinding, microwaves, magnetic fields, electric fields, and continuous attempts of precursor and solution systems, various industrial technologies for preparing alumina powder with respective characteristics are formed. Among them, solvothermal synthesis is often used to prepare corundum powder, and solvothermal synthesis uses high-boiling organic solvents such as ethylene glycol and glycerol. The process can produce high quality products; high purity and uniform size. In various synthesis processes, seed crystals, such as α -Al2O3, α -Fe2O3, or AlF3, are often used to reduce the reaction temperature and product particle size of the synthesized α alumina powder. They have the same structure as alpha alumina, providing low energy sites for heterogeneous nucleation, thereby reducing the energy barrier required for nucleation, and thus lowering the temperature required for reaction, while also avoiding sintering growth of particles at high temperatures.

However, in terms of industrial production, even if the effect of adding seed crystals is achieved, the reaction time required by solvothermal reaction is too long and the temperature is higher, so that the use safety of the reaction kettle is affected. If boehmite or gibbsite is used to physically mix with seed crystal and then calcined at low temperature, although alpha alumina phase can be obtained, in the process of mass mixing production of precursor, the non-uniformly mixed part can cause unstable product quality, part of precursor cannot be converted into alpha alumina phase at low temperature calcination, and for the application of alpha alumina in PET ceramic membrane of lithium ion battery, mesoporous structure is usually needed.

Therefore, how to provide a preparation method of spherical alumina powder can solve the technical problems of difficult control of particle size and shape, easy agglomeration, difficult dispersion, regulation and control of mesoporous and microporous structures and the like, and the technical problems are needed to be solved.

Disclosure of Invention

Aiming at the prior art, the invention provides a preparation method of spherical alumina powder, which is realized by the following steps:

(1) The soluble aluminum salt and the surfactant are dissolved in water by stirring to form a saturated solution a.

(2) The absolute ethyl alcohol and the polyol are mutually dissolved to form an organic solution system B with the polyol concentration of 10-60 percent (volume ratio).

(3) And (3) adding one of formamide, urea and tetramethyl ammonium bicarbonate into the organic solution system B formed in the step (2), and stirring and dissolving to form an organic solution system C.

(4) Adding alumina seed crystal with particle size of 10-50 nm into the organic solution system C obtained in the step (3), and stirring at high speed to form stable suspension D.

(5) And (3) adding the saturated solution A formed in the step (1) and the stable suspension D obtained in the step (4) into a reaction kettle at the same time, wherein the ratio of the saturated solution A to the stable suspension D is 1:2-5 (volume ratio).

(6) Heating the hydrothermal reaction kettle to 60-180 ℃, keeping the temperature for 1-5 hours, and then cooling to room temperature.

(7) And (3) carrying out solid-liquid separation on the reaction product in the step (6), and repeatedly washing with absolute ethyl alcohol for 2-3 times.

(8) Drying the reaction product, calcining at 500-900 ℃ for 5-15 hours to obtain spherical alumina powder with good crystallinity, dispersing the powder in 0.1-10% sulfuric acid solution for 10-20 hours, filtering, washing and drying to obtain spherical alumina powder with narrow particle size distribution and good dispersibility.

Preferably, the soluble aluminum salt in the step (1) comprises any one or two of inorganic compound aluminum nitrate and aluminum sulfate, and the surfactant is sodium dodecyl benzene sulfonate. The mass ratio of the soluble salt source, the surfactant and the water is 5-10:1:10-30.

Preferably, the polyol in step (2) comprises one of ethylene glycol, glycerol, isopropanol, and 1, 4-butanediol.

Preferably, in the step (3), one of formamide, urea and tetramethyl ammonium bicarbonate is added in an amount of 1-10% of the mass of the organic solution system B (mass ratio).

Preferably, the seed crystal addition amount in the step (4) is 5-50% (mass ratio) of the mass of the intermediate boehmite, and the stirring speed is 900-4000rpm.

Compared with the prior art, the invention has the following beneficial effects:

in the solvothermal reaction process, the shape, size, particle size distribution and dispersion effect of the alumina can be effectively controlled by regulating and controlling the sizes and mass ratio of the aluminum salt, the polyol and the nano alumina seed crystal and the solvothermal reaction condition and calcining temperature.

An important technology of the invention is that the viscosity of the polyol is rapidly reduced under the hydrothermal condition and high temperature, the precipitation reaction of aluminum salt is promoted, and after the reaction is completed, the viscosity of the polyol is increased along with the reduction of the temperature, so that the agglomeration of reaction intermediate products is inhibited. Meanwhile, the polyol can be reused through a subsequent distillation process, so that the preparation cost can be greatly reduced.

Another important feature of the present invention is that the process comprises a solvothermal synthesis reaction and a low temperature calcination, wherein the product of the synthesis reaction has a core-shell like structure and high dispersibility between particles. The close and uniform contact of boehmite phase and seed crystal in the core-shell-like structure can reduce the phase transition temperature in the calcination process, meanwhile, the surfactant is used as a soft template, the-Na of the surfactant is replaced by-H to form oiliness under the action of polyalcohol, the soluble aluminum salt is mainly concentrated at an oil/water interface, and the oil drop temporarily serves as a core, so that the synthesis reaction process is not uniform, and a mesoporous structure is formed in the particle through the change of local environment, so that the spherical alumina core structure is a microporous pore canal and the shell structure is a mesoporous structure, and the application of the spherical alumina core structure in the PET ceramic diaphragm of the lithium ion battery is facilitated.

Drawings

FIG. 1 is a TEM and SEM image of spherical alumina powder prepared in example 1;

fig. 2 is a nitrogen adsorption-desorption isotherm plot of the spherical alumina powder prepared in example 1.

Detailed Description

The implementation of the technical solution of the present invention and the advantages thereof will be described in detail by the following specific examples, but should not be construed as limiting the scope of the implementation of the present invention.

Example 1

12 g of aluminum nitrate and 2 g of sodium dodecylbenzenesulfonate were dissolved in 15 ml of absolute ethanol solution by stirring to form solution A. 15 ml of absolute ethanol and 25 ml of 1,4 butanediol are mutually dissolved to form an organic solution system B. 4.0 g of urea was added to the organic solution system B and dissolved with stirring to form an organic solution system C. Subsequently 3 g of alpha alumina seed is added to system C, forming a stable suspension D under high speed stirring. Solution a and suspension D were added simultaneously to the reaction vessel, the reaction vessel was warmed to 180 ℃ at a rate of 5 ℃/min for 5 hours, and then cooled to room temperature. And (3) carrying out solid-liquid separation on the reaction product in the reaction kettle, and repeatedly washing with absolute ethyl alcohol for 2 times. The reaction product was dried and calcined at 800℃for 10 hours to obtain alumina powder having good crystallinity. The powder was dispersed in a 1% sulfuric acid solution for 10 hours, and filtered, washed and dried to obtain alpha alumina powder.

The surface of the alumina obtained in this way is shown to be a mesoporous structure by a high-power projection electron microscope (see figure 1A), the alumina particles obtained by scanning electron microscope are shown to be spherical (see figure 1A 1), and the alumina particles not only have the mesoporous structure but also have micropore channels to prove that the alumina particles have a core-shell-like structure, wherein a core layer has micropore channels, and a shell layer has mesopore channels.

Example 2

An α alumina powder was prepared in the same manner as in example 1, except that butanediol was replaced with 20 ml of ethylene glycol.

The alpha alumina particles prepared by the method are plate-shaped particles with distinct edges and corners, the diameter of the particles is 5-15 microns, the thickness of the particles is about 1 micron, and the redispersibility in water is good.

Comparative example 1

An alpha alumina powder was prepared in the same manner as in example 1 except that 0 g of alpha alumina seed was used, and thus an alumina product was prepared without alpha phase alumina.

Comparative example 2

An α -alumina powder was prepared in the same manner as in example 1 except that 4 g of P123 was used instead of sodium dodecylbenzenesulfonate, and thus an alumina product was prepared without mesoporous channels.

Comparative example 3

3 grams of boehmite was mixed with 0.03 grams of alpha alumina seed using conventional mechanical mixing methods except that the same calcination and treatment process as in example 1 was used, omitting the solvothermal reaction process. The obtained alumina powder is tested by X-ray diffraction analysis, and diffraction peaks not only have alpha alumina peaks, but also contain partial impurity peaks, and the morphology of the alumina powder is characterized by not being completely converted gamma alumina, and comprises platy shapes, spheroid shapes and the like.

Comparative example 1 was not effective in preparing the alpha alumina phase in the absence of seed crystals. The mesoporous pores cannot be formed after the surfactant is replaced in comparative example 2. The limitation of the mixing method of comparative example 3 is that boehmite cannot be uniformly and closely contacted with the seed, so that the entire transformation of the crystalline form cannot be effectively completed in a limited temperature range.

Claims

1. A preparation method of spherical alumina powder is characterized in that: the method is realized by the following steps:

(1) Dissolving soluble aluminum salt and sodium dodecyl benzene sulfonate in water by stirring to form saturated solution A;

(2) The method comprises the steps of (1) mutually dissolving absolute ethyl alcohol and polyalcohol to form an organic solution system B with the polyalcohol concentration of 10-60% in volume ratio, wherein the polyalcohol is one of ethylene glycol, glycerol and 1, 4-butanediol;

(3) Adding one of formamide, urea and tetramethyl ammonium bicarbonate into the organic solution system B formed in the step (2), and stirring and dissolving to form an organic solution system C;

(4) Adding alumina seed crystal with the particle size of 10-50 nanometers into the organic solution system C obtained in the step (3), and stirring at a high speed to form stable suspension D;

(5) Adding the saturated solution A formed in the step (1) and the stable suspension D obtained in the step (4) into a reaction kettle at the same time, wherein the ratio of the saturated solution A to the stable suspension D is 1:2-5 by volume;

(6) Heating the hydrothermal reaction kettle to 60-180 ℃, keeping the temperature for 1-5 hours, and then cooling to room temperature;

(7) Carrying out solid-liquid separation on the reaction product in the step (6), and repeatedly washing with absolute ethyl alcohol for 2-3 times;

2. The method for preparing spherical alumina powder according to claim 1, wherein: the soluble aluminum salt in the step (1) is any one or two of inorganic compounds aluminum nitrate and aluminum sulfate.

3. The method for preparing spherical alumina powder according to claim 2, wherein: the mass ratio of the soluble aluminum salt, sodium dodecyl benzene sulfonate and water is 5-10:1:10-30.

4. The method for preparing spherical alumina powder according to claim 1, wherein: in the step (3), the addition amount of one of formamide, urea and tetramethyl ammonium bicarbonate is 1-10% of the mass of the organic solution system B.

5. The method for preparing spherical alumina powder according to claim 1, wherein: the seed crystal adding amount in the step (4) is 5-50% of the mass of the boehmite of the intermediate product, and the stirring speed is 900-4000rpm.