CN116002734B - A production process for high-purity and high-dispersion nano-alumina - Google Patents

Abstract

The invention discloses a production process of high-purity and high-dispersibility nano-alumina, comprising: preparing hydrated alumina precipitate by hydrolysis of aluminum salt, adding dispersant A to the hydrated alumina precipitate, adjusting the pH of the system to alkaline, and obtaining hydrated alumina slurry after ultrasonic dispersion; hydrothermally refining the hydrated alumina slurry at high temperature and high pressure to obtain nano-hydrated alumina slurry, cooling, aging, solid-liquid separation, putting the nano-hydrated alumina slurry obtained by washing and filtering into ethylene glycol solution, heating, adding dispersant B to the ethylene glycol solution, ultrasonic dispersion, and obtaining nano-hydrated alumina dispersed slurry; solid-liquid separation to obtain nano-hydrated alumina dispersed slurry, washing, filtering, and drying to obtain nano-hydrated alumina solid powder; using high-pressure nitrogen or carbon dioxide to counterbalance and vacuum roasting to obtain nano-hydrated alumina powder. The nano-hydrated alumina prepared by the invention has the characteristics of good dispersibility and high purity, and can be used to prepare alumina ceramic substrates.

Description

A production process for high-purity and high-dispersion nano-alumina

Technical Field

The invention belongs to the technical field of ceramic powder preparation, and more specifically, relates to a production process of high-purity and high-dispersity nano-grade aluminum oxide.

Background Art

Nano-alumina has many excellent properties, such as high thermal conductivity, high insulation, high hardness, high temperature resistance, corrosion resistance, wear resistance, etc. Nano-alumina powder is mainly used as raw material powder for alumina ceramic substrates, and alumina ceramic substrates are mainly used for chip resistor LED packaging. At present, the main methods for preparing nano-alumina are alcohol aluminum method, thermal decomposition method, amorphous crystallization method, sol-gel method, liquid phase precipitation method, etc. Among them, alcohol aluminum method is the most widely used method for preparing alumina in industry.

The purity and dispersibility of nano-alumina powder affect the quality of the prepared alumina ceramic substrate. The preparation of ceramic substrate generally requires high-purity nano-alumina powder with a purity of more than 99.7%. At the same time, the uniformity of the dispersibility and particle size distribution of nano-alumina is also extremely high. The thermal conductivity, thermal expansion coefficient and bending strength mechanical properties of the power ceramic substrate obtained by sintering the nano-alumina powder with high purity and good dispersibility are more excellent. This is because the alumina powder with a smaller particle size can be pressed and sintered to obtain a denser power ceramic substrate, which makes the heating growth of the power ceramic substrate lower and more suitable as a high-temperature resistant insulating material, and there are fewer defects such as pores between the alumina phases. At present, the dispersibility of the alumina powder prepared by the alcohol aluminum method is not ideal, and the particle size distribution of the alumina powder is not concentrated enough. In order to prepare nano-alumina powder with high purity, high dispersibility and concentrated particle size distribution to meet the sintering preparation of high thermal conductivity, low thermal expansion coefficient and high bending strength power ceramic substrate, it is necessary to improve the current nano-alumina production process.

Summary of the invention

An object of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages which will be described hereinafter.

In order to achieve these purposes and other advantages according to the present invention, a production process of high-purity, high-dispersity nano-scale aluminum oxide is provided, comprising:

Step 1: Hydrolyze aluminum salt to obtain hydrated aluminum oxide precipitate, add dispersant A to the hydrated aluminum oxide precipitate, adjust the pH of the system to alkaline after dispersion, and obtain hydrated aluminum oxide slurry after ultrasonic dispersion;

Step 2: hydrothermally refine the hydrated alumina slurry at high temperature and high pressure to obtain nano hydrated alumina slurry, cool and age it, perform solid-liquid separation, add the washed and filtered nano hydrated alumina slurry to a 2-12%wt ethylene glycol solution, heat it, add dispersant B to the ethylene glycol solution and perform ultrasonic dispersion to obtain nano hydrated alumina dispersed slurry;

Step 3: solid-liquid separation to obtain nano-hydrated alumina dispersion slurry, washing, filtering, and drying to obtain nano-hydrated alumina solid powder; the nano-hydrated alumina solid powder is flushed with high-pressure nitrogen or carbon dioxide, and then vacuum-calcined to obtain nano-grade alumina powder.

Preferably, in step 1, the aluminum salt is one of aluminum isopropoxide, aluminum ethoxide, aluminum methoxide, aluminum propoxide, aluminum hexoxide and aluminum dipentoxide.

Preferably, the dispersant A in step 1 is a mixed dispersant composed of polyethylene glycol, citric acid and tetramethyldisilazane in a mass ratio of 3:1:1-2, and the amount of dispersant A is 0.4-12% of the mass of the aluminum salt.

Preferably, in the step 1, after adding dispersant A, stirring is performed at a speed of 300 to 450 r/min for 15 to 40 min; the method for adjusting the pH of the system to alkaline is to add sodium hydroxide to the system to adjust the pH to 8 to 10; the frequency of ultrasonic dispersion is 45 to 80 kHz, and the dispersion time is 35 to 55 min.

Preferably, in the step 2, the method of hydrothermally refining the hydrated alumina slurry at high temperature and high pressure to obtain nano hydrated alumina slurry comprises: heating the temperature of the hydrated alumina slurry to 60-95°C at a heating rate of 5-8°C/min, stirring at a speed of 600-800r/min for 10-15min and then keeping warm for 1-2h; adding ammonium bicarbonate to the reactor in an amount of 4-10% of the mass of the aluminum salt, and then heating to 180-225°C at a heating rate of 10-15°C/min, pressurizing the reactor to 2-3.6Mpa, and maintaining constant pressure and temperature for 2-4h to obtain nano hydrated alumina slurry.

Preferably, the aging temperature in step 2 is 25-32° C., and the aging time is 5-20 h.

Preferably, in the step 2, the dispersant B used is a blended modified dispersant of polyvinyl alcohol, urea and polyethylene glycol-200, and the amount of dispersant B is 5-10% of the mass of the aluminum salt; the preparation method of dispersant B comprises: weighing 12-25 parts of polyvinyl alcohol by weight, heating 60-80 parts of deionized water to above 95°C, then adding polyvinyl alcohol, stirring until the polyvinyl alcohol is completely dissolved, cooling the solution to 40°C, adding 0.5-2 parts of urea, stirring to dissolve, and keeping warm for 20-60 minutes to obtain a mixed solution; after the temperature of the mixed solution drops to 25°C, adding 1.5-4 parts of polyethylene glycol-200, stirring to dissolve, and standing for 1-2 hours to obtain a dispersant solution; in a nitrogen atmosphere, heating and evaporating the deionized water in the dispersant solution to obtain dispersant B.

Preferably, in the step three, ethanol is used to wash the nano-hydrated alumina dispersion slurry, and the drying temperature is 120-140°C.

Preferably, in the step three, the specific method of flushing the nano hydrated alumina solid powder with high-pressure nitrogen or carbon dioxide is: using two injectors arranged horizontally relative to each other, one of which sprays high-pressure nitrogen or carbon dioxide, and the other injects the nano hydrated alumina solid powder, and the nano hydrated alumina solid powder is further atomized and dispersed by the high-pressure nitrogen or carbon dioxide; wherein the pressure of the nitrogen and carbon dioxide in the injector is 30 to 40 kPa, and the pressure of the nano hydrated alumina solid powder is 10 to 15 kPa.

Preferably, in the step three, the calcination temperature of the nano-alumina powder obtained by vacuum calcination is 500-800°C, the vacuum degree during calcination is less than 2.5× ^10-4 Pa, and the calcination time is 1-3h.

The present invention at least includes the following beneficial effects: the nano-alumina prepared by the present invention has the characteristics of good dispersibility, high purity and concentrated particle size distribution, and can be used as raw material powder for alumina ceramic substrates.

In the process of preparing nano-alumina powder, the present invention uses the alcohol aluminum method, and no impurities are introduced in the processes of hydrolysis, dispersion, hedging and roasting. The reagents used are all soluble in deionized water or ethanol and can be removed in the slurry by washing, so that the finally prepared nano-alumina powder has high purity, and the purity can reach more than 99.7%.

The present invention maintains the dispersibility of the hydrated alumina slurry throughout the entire process of preparing the nano-alumina powder. In the early stage, a dispersant A is used to disperse the hydrated alumina precipitate obtained by hydrolysis. When the nano-hydrated alumina slurry is obtained by high-temperature and high-pressure hydrothermal refinement, ammonium bicarbonate is added to the system. The ammonia and carbon dioxide released by the thermal decomposition of the ammonium bicarbonate act on the hydrated alumina slurry, which not only makes the reaction more complete, but also forms a dispersing effect on the hydrated alumina slurry, thereby ensuring the dispersibility of the hydrated alumina slurry during the hydrothermal refinement. The hydrated alumina slurry is subjected to high-temperature and high-pressure hydrothermal refinement to obtain the nano-hydrated alumina slurry. After the alumina hydrate slurry is prepared, ethanol and dispersant B are used to disperse the slurry; when the nano-alumina powder is finally obtained, high-pressure nitrogen and carbon dioxide are first used to hedge the nano-hydrated alumina solid powder. Compared with conventional liquid hedge, high-pressure gas hedge has a higher pressure and has a better dispersion effect on the nano-hydrated alumina solid powder. At the same time, the nano-hydrated alumina solid powder does not need to be separated from the solid and liquid and washed and dried in the later stage, which simplifies the process and reduces the production cost; finally, the nano-hydrated alumina solid powder is dehydrated by vacuum roasting to obtain the nano-scale alumina powder.

Dispersant A is made of polyethylene glycol, citric acid and tetramethyldisilazane as main raw materials, and dispersant B is modified by blending polyvinyl alcohol, urea and polyethylene glycol-200. As a result, the slurry whose surface is dispersed by dispersant B greatly reduces the agglomeration of nano hydrated alumina in the slurry and improves the dispersibility of nano hydrated alumina. Dispersants A and B are both easily soluble in water and easy to separate from the slurry, so they will not bring impurities to the product, thereby ensuring the purity of the nano alumina.

Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention.

DETAILED DESCRIPTION

The present invention is described in further detail below so that those skilled in the art can implement it according to the description.

It should be understood that terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

Example 1

This embodiment provides a production process of high-purity and high-dispersibility nano-alumina, comprising the following steps:

Step 1: hydrolyze 1 kg of aluminum isopropoxide to obtain a hydrated alumina precipitate, add dispersant A to the hydrated alumina precipitate, stir at a speed of 300 r/min for 15 min, add sodium hydroxide to the system after dispersion to adjust the pH of the system to 8, and ultrasonically disperse at a frequency of 45 kHz for 35 min to obtain a hydrated alumina slurry; wherein the dispersant A includes 2.4 g of polyethylene glycol, 0.8 g of citric acid and 0.8 g of tetramethyldisilazane;

Step 2, heating the temperature of the hydrated alumina slurry to 60°C at a heating rate of 5°C/min, stirring at a speed of 600r/min for 10min and then keeping warm for 1h; adding 40g of ammonium bicarbonate to the reactor, and then heating it to 180°C at a heating rate of 10°C/min, pressurizing the reactor to 2Mpa, maintaining constant pressure and temperature for 2h to obtain nano hydrated alumina slurry, cooling, and aging at 25°C for 5h, then performing solid-liquid separation, and putting the washed and filtered nano hydrated alumina slurry into a 2%wt ethylene glycol solution, heating, and adding 50g of dispersant B to the ethylene glycol solution for ultrasonic dispersion to obtain nano hydrated alumina dispersed slurry; The dispersant B used is a blended modified dispersant of polyvinyl alcohol, urea and polyethylene glycol-200; the preparation method of dispersant B comprises: weighing 120g of polyvinyl alcohol by weight, heating 600g of deionized water to above 95°C, then adding polyvinyl alcohol, stirring until the polyvinyl alcohol is completely dissolved, cooling the solution to 40°C, adding 5g of urea, stirring to dissolve, and keeping warm for 20min to obtain a mixed solution; after the temperature of the mixed solution drops to 25°C, adding 15g of polyethylene glycol-200, stirring to dissolve, and standing for 1h to obtain a dispersant solution; in a nitrogen atmosphere, heating to completely evaporate the deionized water in the dispersant solution to obtain dispersant B;

Step 3: separate the nano-hydrated alumina dispersion slurry by solid-liquid separation, wash with ethanol, filter, and dry at 120°C to obtain nano-hydrated alumina solid powder; use high-pressure nitrogen to counteract the nano-hydrated alumina solid powder, specifically, use two horizontally oppositely arranged injectors, one of which sprays high-pressure nitrogen, and the other injects the nano-hydrated alumina solid powder, and the nano-hydrated alumina solid powder is further atomized and dispersed by the high-pressure nitrogen; wherein the nitrogen pressure of the injector is 30kPa, and the pressure of the nano-hydrated alumina solid powder is 10kPa; then vacuum calcination is performed to obtain nano-scale alumina powder, the vacuum calcination temperature is 500°C, the vacuum degree during calcination is less than 2.5× ^10-4 Pa, and the calcination time is 1h.

Example 2

This embodiment provides a production process of high-purity and high-dispersibility nano-alumina, comprising the following steps:

Step 1: hydrolyze 1 kg of aluminum isopropoxide to obtain a hydrated alumina precipitate, add dispersant A to the hydrated alumina precipitate, stir at a speed of 350 r/min for 20 min, add sodium hydroxide to the system after dispersion to adjust the pH of the system to 8, and ultrasonically disperse at a frequency of 50 kHz for 40 min to obtain a hydrated alumina slurry; wherein the dispersant A includes 6 g of polyethylene glycol, 2 g of citric acid and 2 g of tetramethyldisilazane;

Step 2: Raise the temperature of the hydrated alumina slurry to 70°C at a heating rate of 6°C/min, stir at a speed of 600r/min for 10min, and then keep warm for 1h; add 50g of ammonium bicarbonate to the reactor, and then raise the temperature to 200°C at a heating rate of 12°C/min, pressurize the reactor to 2.2Mpa, maintain constant pressure and temperature for 2h, and obtain nano hydrated alumina slurry; cool it, and age it at 25°C for 6h, then perform solid-liquid separation, and put the washed and filtered nano hydrated alumina slurry into a 5%wt ethylene glycol solution, heat it, and add 60g of dispersant B to the ethylene glycol solution for ultrasonic dispersion to obtain nano hydrated alumina dispersed slurry. ; Wherein, the dispersant B used is a blended modified dispersant of polyvinyl alcohol, urea and polyethylene glycol-200; wherein, the preparation method of dispersant B comprises: weighing 150g of polyvinyl alcohol by weight, heating 700g of deionized water to above 95°C, then adding polyvinyl alcohol, stirring until the polyvinyl alcohol is completely dissolved, cooling the solution to 40°C, adding 10g of urea, stirring to dissolve, and keeping warm for 30min to obtain a mixed solution; after the temperature of the mixed solution drops to 25°C, adding 20g of polyethylene glycol-200, stirring to dissolve, and standing for 1h to obtain a dispersant solution; in a nitrogen atmosphere, heating to completely evaporate the deionized water in the dispersant solution to obtain dispersant B;

Step 3: separate the nano-hydrated alumina dispersion slurry by solid-liquid separation, wash with ethanol, filter, and dry at 130°C to obtain nano-hydrated alumina solid powder; use high pressure to counter-punch the nano-hydrated alumina solid powder, specifically, use two horizontally oppositely arranged injectors, one of which sprays high-pressure nitrogen, and the other injects the nano-hydrated alumina solid powder, and the nano-hydrated alumina solid powder is further atomized and dispersed by the high-pressure nitrogen; wherein the nitrogen pressure of the injector is 32kPa, and the pressure of the nano-hydrated alumina solid powder is 10kPa; then vacuum calcination is performed to obtain nano-grade alumina powder, the vacuum calcination temperature is 600°C, the vacuum degree during calcination is less than 2.5× ^10-4 Pa, and the calcination time is 1h.

Example 3

This embodiment provides a production process of high-purity and high-dispersibility nano-alumina, comprising the following steps:

Step 1: hydrolyze 1 kg of aluminum isopropoxide to obtain a hydrated alumina precipitate, add dispersant A to the hydrated alumina precipitate, stir at a speed of 400 r/min for 30 min, add sodium hydroxide to the system after dispersion to adjust the pH of the system to 9, and ultrasonically disperse at a frequency of 70 kHz for 50 min to obtain a hydrated alumina slurry; wherein the dispersant A includes 30 g of polyethylene glycol, 20 g of citric acid and 20 g of tetramethyldisilazane;

Step 2: Raise the temperature of the hydrated alumina slurry to 90°C at a heating rate of 7°C/min, stir at a speed of 700r/min for 10min and keep warm for 2h; add 80g of ammonium bicarbonate to the reactor, and then raise the temperature to 210°C at a heating rate of 14°C/min, pressurize the reactor to 3.0Mpa, maintain constant pressure and temperature for 3h to obtain nano hydrated alumina slurry, cool it, and age it at 25°C for 6h before solid-liquid separation, and put the washed and filtered nano hydrated alumina slurry into 8%wt ethylene glycol solution, heat it, add 80g of dispersant B to the ethylene glycol solution for ultrasonic dispersion to obtain nano hydrated alumina dispersed slurry ; Wherein, the dispersant B used is a blended modified dispersant of polyvinyl alcohol, urea and polyethylene glycol-200; wherein, the preparation method of dispersant B comprises: weighing 200g of polyvinyl alcohol by weight, heating 700g of deionized water to above 95°C, then adding polyvinyl alcohol, stirring until the polyvinyl alcohol is completely dissolved, cooling the solution to 40°C, adding 15g of urea, stirring to dissolve, and keeping warm for 40min to obtain a mixed solution; after the temperature of the mixed solution drops to 25°C, adding 25g of polyethylene glycol-200, stirring to dissolve, and standing for 2h to obtain a dispersant solution; in a nitrogen atmosphere, heating to completely evaporate the deionized water in the dispersant solution to obtain dispersant B;

Step 3: separate the nano-hydrated alumina dispersion slurry by solid-liquid separation, wash with ethanol, filter, and dry at 130°C to obtain nano-hydrated alumina solid powder; use high-pressure carbon dioxide to counteract the nano-hydrated alumina solid powder, specifically, use two horizontally oppositely arranged injectors, one of which sprays high-pressure nitrogen, and the other injects the nano-hydrated alumina solid powder, and the nano-hydrated alumina solid powder is further atomized and dispersed by the high-pressure nitrogen; wherein the nitrogen pressure of the injector is 36 kPa, and the pressure of the nano-hydrated alumina solid powder is 13 kPa; then vacuum calcination is performed to obtain nano-grade alumina powder, the vacuum calcination temperature is 700°C, the vacuum degree during calcination is less than 2.5× ^10-4 Pa, and the calcination time is 2 h.

Example 4

This embodiment provides a production process of high-purity and high-dispersibility nano-alumina, comprising the following steps:

Step 1: hydrolyze 1 kg of aluminum isopropoxide to obtain a hydrated alumina precipitate, add dispersant A to the hydrated alumina precipitate, stir at a speed of 450 r/min for 40 min, add sodium hydroxide to the system after dispersion to adjust the pH of the system to 10, and ultrasonically disperse at a frequency of 80 kHz for 55 min to obtain a hydrated alumina slurry; wherein the dispersant A includes 72 g of polyethylene glycol, 48 g of citric acid and 48 g of tetramethyldisilazane;

Step 2, heating the temperature of the hydrated alumina slurry to 95°C at a heating rate of 8°C/min, stirring at a speed of 800r/min for 15min and then keeping warm for 2h; adding 100g of ammonium bicarbonate to the reactor, and then heating it to 225°C at a heating rate of 15°C/min, pressurizing the reactor to 3.6Mpa, maintaining constant pressure and temperature for 4h to obtain nano hydrated alumina slurry, cooling, and aging at 32°C for 20h, then performing solid-liquid separation, and putting the washed and filtered nano hydrated alumina slurry into a 12%wt ethylene glycol solution, heating, adding 100g of dispersant B to the ethylene glycol solution for ultrasonic dispersion, and obtaining nano hydrated alumina dispersion Slurry; wherein the dispersant B used is a blended modified dispersant of polyvinyl alcohol, urea and polyethylene glycol-200; wherein the preparation method of dispersant B comprises: weighing 250g of polyvinyl alcohol by weight, heating 800g of deionized water to above 95°C, then adding polyvinyl alcohol, stirring until the polyvinyl alcohol is completely dissolved, cooling the solution to 40°C, adding 20g of urea, stirring to dissolve, and keeping warm for 60min to obtain a mixed solution; after the temperature of the mixed solution drops to 25°C, adding 40g of polyethylene glycol-200, stirring to dissolve, and standing for 2h to obtain a dispersant solution; in a nitrogen atmosphere, heating to completely evaporate the deionized water in the dispersant solution to obtain dispersant B;

Step 3: separate the nano-hydrated alumina dispersion slurry by solid-liquid separation, wash with ethanol, filter, and dry at 140°C to obtain nano-hydrated alumina solid powder; use high-pressure carbon dioxide to counteract the nano-hydrated alumina solid powder, specifically, use two horizontally oppositely arranged injectors, one of which sprays high-pressure nitrogen, and the other injects the nano-hydrated alumina solid powder, and the nano-hydrated alumina solid powder is further atomized and dispersed by the high-pressure nitrogen; wherein the nitrogen pressure of the injector is 40kPa, and the pressure of the nano-hydrated alumina solid powder is 15kPa; then vacuum calcination is performed to obtain nano-scale alumina powder, the vacuum calcination temperature is 800°C, the vacuum degree during calcination is less than 2.5× ^10-4 Pa, and the calcination time is 3h.

Comparative Example 1

This comparative example provides a production process of high-purity nano-aluminum oxide, comprising the following steps:

Step 1: hydrolyze 1 kg of aluminum isopropoxide to obtain a hydrated alumina precipitate, add dispersant A to the hydrated alumina precipitate, stir at a speed of 300 r/min for 15 min, add sodium hydroxide to the system after dispersion to adjust the pH of the system to 8, and ultrasonically disperse at a frequency of 45 kHz for 35 min to obtain a hydrated alumina slurry; wherein the dispersant A includes 2.4 g of polyethylene glycol, 0.8 g of citric acid and 0.8 g of tetramethyldisilazane;

Step 2: Raise the temperature of the hydrated alumina slurry to 60°C at a heating rate of 5°C/min, stir at a speed of 600r/min for 10min and keep warm for 1h; add 40g of ammonium bicarbonate to the reactor, and then raise the temperature to 180°C at a heating rate of 10°C/min, pressurize the reactor to 2Mpa, maintain constant pressure and temperature for 2h to obtain nano hydrated alumina slurry, cool it, and age it at 25°C for 5h, then perform solid-liquid separation, wash and filter the obtained nano hydrated alumina slurry;

Step 3: Wash the nano-hydrated alumina slurry with ethanol, filter it, and dry it at 120°C to obtain a nano-hydrated alumina solid powder; use high-pressure nitrogen to counteract the nano-hydrated alumina solid powder, specifically using two horizontally opposed injectors, one of which sprays high-pressure nitrogen, and the other injects the nano-hydrated alumina solid powder, and the nano-hydrated alumina solid powder is further atomized and dispersed by the high-pressure nitrogen; wherein the nitrogen pressure of the injector is 30kPa, and the pressure of the nano-hydrated alumina solid powder is 10kPa; then vacuum calcination is performed to obtain nano-scale alumina powder, the vacuum calcination temperature is 500°C, the vacuum degree during calcination is less than 2.5× ^10-4 Pa, and the calcination time is 1h.

Comparative Example 2

This comparative example provides a production process of high-purity nano-aluminum oxide, comprising the following steps:

Step 1: hydrolyze 1 kg of aluminum isopropoxide to obtain a hydrated alumina precipitate, add dispersant A to the hydrated alumina precipitate, stir at a speed of 350 r/min for 20 min, add sodium hydroxide to the system after dispersion to adjust the pH of the system to 8, and ultrasonically disperse at a frequency of 50 kHz for 40 min to obtain a hydrated alumina slurry; wherein the dispersant A includes 6 g of polyethylene glycol, 2 g of citric acid and 2 g of tetramethyldisilazane;

Step 2: Raise the temperature of the hydrated alumina slurry to 70°C at a heating rate of 6°C/min, stir at a speed of 600r/min for 10min and keep warm for 1h; add 50g of ammonium bicarbonate to the reactor, and then raise the temperature to 200°C at a heating rate of 12°C/min, pressurize the reactor to 2.2Mpa, maintain constant pressure and temperature for 2h, and obtain nano hydrated alumina slurry; cool it, and age it at 25°C for 6h, then perform solid-liquid separation, wash and filter the obtained nano hydrated alumina slurry

Step 3: The obtained nano-hydrated alumina slurry is washed with ethanol, filtered, and dried at 130°C to obtain nano-hydrated alumina solid powder; the nano-hydrated alumina solid powder is counteracted with high-pressure nitrogen, specifically, two horizontally opposed injectors are used, one of which sprays high-pressure nitrogen, and the other injects the nano-hydrated alumina solid powder, and the nano-hydrated alumina solid powder is further atomized and dispersed by the high-pressure nitrogen; wherein the nitrogen pressure of the injector is 32 kPa, and the pressure of the nano-hydrated alumina solid powder is 10 kPa; and then the nano-scale alumina powder is obtained by vacuum calcination, the vacuum calcination temperature is 600°C, the vacuum degree during calcination is less than 2.5× ^10-4 Pa, and the calcination time is 1 h.

Comparative Example 3

This comparative example provides a production process of high-purity nano-aluminum oxide, comprising the following steps:

Step 1: hydrolyze 1 kg of aluminum isopropoxide to obtain a hydrated alumina precipitate, add dispersant A to the hydrated alumina precipitate, stir at a speed of 300 r/min for 15 min, add sodium hydroxide to the system after dispersion to adjust the pH of the system to 8, and ultrasonically disperse at a frequency of 45 kHz for 35 min to obtain a hydrated alumina slurry; wherein the dispersant A includes 2.4 g of polyethylene glycol, 0.8 g of citric acid and 0.8 g of tetramethyldisilazane;

Step 2: Raise the temperature of the hydrated alumina slurry to 60°C, stir at a speed of 600r/min for 10min and then keep warm for 1h; then raise the temperature to 180°C, pressurize the reactor to 2Mpa, maintain constant pressure and temperature for 2h to obtain nano hydrated alumina slurry, cool it, and age it at 25°C for 5h before solid-liquid separation, and put the washed and filtered nano hydrated alumina slurry into a 2%wt ethylene glycol solution, heat it, and add 50g of dispersant B to the ethylene glycol solution for ultrasonic dispersion to obtain nano hydrated alumina dispersed slurry; wherein the dispersant B used is polyvinyl alcohol, urea and polyvinyl alcohol. A blended modified dispersant of ethylene glycol-200; wherein the preparation method of dispersant B comprises: weighing 120g of polyvinyl alcohol by weight, heating 600g of deionized water to above 95°C, then adding polyvinyl alcohol, stirring until the polyvinyl alcohol is completely dissolved, cooling the solution to 40°C, adding 5g of urea, stirring to dissolve, and keeping warm for 20min to obtain a mixed solution; after the temperature of the mixed solution drops to 25°C, adding 15g of polyethylene glycol-200, stirring to dissolve, and standing for 1h to obtain a dispersant solution; in a nitrogen atmosphere, heating to completely evaporate the deionized water in the dispersant solution to obtain dispersant B;

Step 3: separate the nano-hydrated alumina dispersion slurry by solid-liquid separation, wash with ethanol, filter, and dry at 120°C to obtain nano-hydrated alumina solid powder; use high-pressure nitrogen to counteract the nano-hydrated alumina solid powder, specifically, use two horizontally oppositely arranged injectors, one of which sprays high-pressure nitrogen, and the other injects the nano-hydrated alumina solid powder, and the nano-hydrated alumina solid powder is further atomized and dispersed by the high-pressure nitrogen; wherein the nitrogen pressure of the injector is 30kPa, and the pressure of the nano-hydrated alumina solid powder is 10kPa; then vacuum calcination is performed to obtain nano-scale alumina powder, the vacuum calcination temperature is 500°C, the vacuum degree during calcination is less than 2.5× ^10-4 Pa, and the calcination time is 1h.

Comparative Example 4

This comparative example provides a production process of high-purity nano-aluminum oxide, comprising the following steps:

Step 1: hydrolyze 1 kg of aluminum isopropoxide to obtain a hydrated alumina precipitate, add dispersant A to the hydrated alumina precipitate, stir at a speed of 300 r/min for 15 min, add sodium hydroxide to the system after dispersion to adjust the pH of the system to 8, and ultrasonically disperse at a frequency of 45 kHz for 35 min to obtain a hydrated alumina slurry; wherein the dispersant A includes 2.4 g of polyethylene glycol, 0.8 g of citric acid and 0.8 g of tetramethyldisilazane;

Step 2, heating the temperature of the hydrated alumina slurry to 60°C at a heating rate of 5°C/min, stirring at a speed of 600r/min for 10min and then keeping warm for 1h; adding 40g of ammonium bicarbonate to the reactor, and then heating it to 180°C at a heating rate of 10°C/min, pressurizing the reactor to 2Mpa, maintaining constant pressure and temperature for 2h to obtain nano hydrated alumina slurry, cooling, and aging at 25°C for 5h, then performing solid-liquid separation, and putting the washed and filtered nano hydrated alumina slurry into a 2%wt ethylene glycol solution, heating, and adding 50g of dispersant B to the ethylene glycol solution for ultrasonic dispersion to obtain nano hydrated alumina dispersed slurry; The dispersant B used is a blended modified dispersant of polyvinyl alcohol, urea and polyethylene glycol-200; the preparation method of dispersant B comprises: weighing 120g of polyvinyl alcohol by weight, heating 600g of deionized water to above 95°C, then adding polyvinyl alcohol, stirring until the polyvinyl alcohol is completely dissolved, cooling the solution to 40°C, adding 5g of urea, stirring to dissolve, and keeping warm for 20min to obtain a mixed solution; after the temperature of the mixed solution drops to 25°C, adding 15g of polyethylene glycol-200, stirring to dissolve, and standing for 1h to obtain a dispersant solution; in a nitrogen atmosphere, heating to completely evaporate the deionized water in the dispersant solution to obtain dispersant B;

Step 3: Separate the nano-hydrated alumina dispersion slurry by solid-liquid separation, wash with ethanol, filter, and dry at 120°C to obtain nano-hydrated alumina solid powder; and obtain nano-scale alumina powder by vacuum calcination. The vacuum calcination temperature is 500°C, the vacuum degree during calcination is less than 2.5× ^10-4 Pa, and the calcination time is 1h.

The average particle size D50 of the high-purity, high-dispersibility nano-alumina powders obtained in Examples 1 to 4 and the high-purity nano-alumina powders obtained in Comparative Examples 1 to 4, as well as the thermal conductivity, thermal expansion coefficient and flexural strength of the power package substrate samples sintered using the nano-alumina powders of Examples 1 to 4 and Comparative Examples 1 to 4 were measured respectively, wherein the sintering temperature of each sample was 1600° C. and the holding time was 6 hours, and the following table was obtained:

As can be seen from the above table, the nano-alumina ceramics obtained by the production process of high-purity and high-dispersity nano-alumina provided by the present invention in Examples 1 to 4 have smaller particle sizes and better dispersibility, so that the power ceramic substrate obtained after sintering has fewer defects such as bulk pores, and the powders of the power ceramic substrate obtained after sintering are denser, thereby having a higher thermal conductivity coefficient, a lower thermal expansion coefficient and a greater bending strength.

The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the present invention will be obvious to those skilled in the art.

Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the examples shown and described herein.

Claims (7)

1. The production process of the high-purity high-dispersibility nanoscale alumina is characterized by comprising the following steps of:

Firstly, hydrolyzing aluminum salt to prepare hydrated alumina precipitate, adding a dispersing agent A into the hydrated alumina precipitate, adjusting the pH value of the system to be alkaline after dispersing, and obtaining hydrated alumina slurry after ultrasonic dispersion;

Carrying out high-temperature high-pressure hydrothermal refinement on the hydrated alumina slurry to obtain nano hydrated alumina slurry, cooling, aging, carrying out solid-liquid separation, putting the washed and filtered nano hydrated alumina slurry into a glycol solution with the weight of 2-12%, heating, adding a dispersing agent B into the glycol solution, and carrying out ultrasonic dispersion to obtain nano hydrated alumina dispersion slurry;

Step three, separating solid and liquid to obtain nano hydrated alumina dispersion slurry, and washing, filtering and drying to obtain nano hydrated alumina solid powder; the nano hydrated alumina solid powder is hedged by high-pressure nitrogen or carbon dioxide, and then the nano hydrated alumina solid powder is obtained by vacuum roasting;

the dispersing agent A in the first step is a mixed dispersing agent composed of polyethylene glycol, citric acid and tetramethyl disilazane according to a mass ratio of 3:1:1-2, and the consumption of the dispersing agent A is 0.4-12% of the mass of aluminum salt;

In the first step, after adding the dispersing agent A, stirring for 15-40 min at the rotating speed of 300-450 r/min; the method for adjusting the pH value of the system to be alkaline comprises the steps of adding sodium hydroxide into the system to adjust the pH value to 8-10; the ultrasonic dispersion frequency is 45-80 kHz, and the dispersion time is 35-55 min;

in the second step, the used dispersing agent B is a blending modified dispersing agent of polyvinyl alcohol, urea and polyethylene glycol-200, and the dosage of the dispersing agent B is 5-10% of the mass of aluminum salt; the preparation method of the dispersant B comprises the following steps: weighing 12-25 parts by weight of polyvinyl alcohol, heating 60-80 parts by weight of deionized water to above 95 ℃, then adding the polyvinyl alcohol, stirring until the polyvinyl alcohol is completely dissolved, cooling the solution to 40 ℃, adding 0.5-2 parts by weight of urea, stirring and dissolving, and preserving heat for 20-60 min to obtain a mixed solution; after the temperature of the mixed solution is reduced to 25 ℃, adding 1.5-4 parts of polyethylene glycol-200, stirring and dissolving, and standing for 1-2 hours to obtain a dispersing agent solution; and in a nitrogen atmosphere, heating and evaporating deionized water in the complete dispersing agent solution to obtain a dispersing agent B.

2. The process for producing high purity, high dispersibility nano-sized alumina according to claim 1, wherein in the first step, the aluminum salt is one of aluminum isopropoxide, aluminum ethoxide, aluminum methoxide, aluminum propoxide, aluminum hexanoxide and aluminum dipentaerythritol.

3. The process for producing high purity, high dispersibility nano-scale alumina according to claim 1, wherein in the second step, the method for obtaining nano-alumina hydrate slurry by high temperature and high pressure hydrothermal refining of the alumina hydrate slurry comprises: heating the hydrated alumina slurry to 60-95 ℃ at a heating rate of 5-8 ℃/min, stirring at a speed of 600-800 r/min for 10-15 min, and then preserving heat for 1-2 h; and adding ammonium bicarbonate into the reaction kettle, wherein the adding amount is 4-10% of the mass of the aluminum salt, heating to 180-225 ℃ at a heating rate of 10-15 ℃/min, pressurizing the reaction kettle to 2-3.6 mpa, and maintaining constant pressure and temperature for 2-4 h to obtain the nano hydrated alumina slurry.

4. The process for producing high purity, high dispersibility nano-scale alumina according to claim 1, wherein the aging temperature in the second step is 25 to 32 ℃ and the aging time is 5 to 20 hours.

5. The process for producing high purity and high dispersibility nano-sized alumina according to claim 1, wherein in the third step, ethanol is used to wash the nano-sized alumina hydrate dispersion slurry, and the drying temperature is 120-140 ℃.

6. The process for producing high purity, high dispersibility nano-scale alumina according to claim 1, wherein in the third step, the specific method for using high pressure nitrogen or carbon dioxide for hedging the nano-alumina hydrate solid powder is as follows: two ejectors which are horizontally arranged oppositely are adopted, wherein one ejector ejects high-pressure nitrogen or carbon dioxide, the other ejector ejects nano-alumina hydrate solid powder, and the nano-alumina hydrate solid powder is further atomized and dispersed through the high-pressure nitrogen or the carbon dioxide; the pressurization of nitrogen and carbon dioxide is 30-40 kPa, and the pressurization of the nano-alumina hydrate solid powder is 10-15 kPa.

7. The process for producing high purity, high dispersibility nano-scale alumina according to claim 1, wherein in the third step, the roasting temperature of the nano-scale alumina powder obtained by vacuum roasting is 500-800 ℃, the vacuum degree during roasting is less than 2.5X10- ^﹣4 Pa, and the roasting time is 1-3 hours.