Method for preparing alpha-Al2O3 through direct hydrolysis of Ga-In melt activated aluminum

Abstract

The invention relates to a method for preparing alpha-Al2O3 through direct hydrolysis of Ga-In melt activated aluminum, and belongs to the technical field of aluminum oxide preparation. The Ga-In alloy melt is used for activating aluminum, the activating mode is simple and efficient, and aluminum can react with water at normal temperature and normal pressure. In the hydrolysis process, the Ga-In alloy can be agglomerated and settled to the bottom through long-time stirring, most Ga-In metal is removed, and the Ga-In alloy can be recycled. And carrying out secondary calcination treatment to finally obtain the high-purity alpha-Al2O3.

Description

Technical Field

[0001] This invention relates to a method for preparing α-Al2O3 by direct hydrolysis of activated aluminum in Ga-In melt, belonging to the field of alumina preparation technology. Background Technology

[0002] High-purity alumina, as a key basic material in modern industry, directly affects the quality level of high-end products such as precision ceramic devices, semiconductor substrates, and laser crystals. Due to its unique physical and chemical properties, such as high strength, lightweight, high temperature resistance, and excellent optical properties, high-purity alumina is considered an important raw material in many industries.

[0003] Direct hydrolysis of molten aluminum is a novel method for preparing high-purity alumina. This method is simple and highly efficient. Because of the dense alumina layer on the surface of aluminum, it cannot react with water at room temperature and pressure, and reactions in acidic or alkaline solutions pose safety hazards. Therefore, aluminum needs to be activated to allow it to react spontaneously with water at room temperature and pressure. Traditional activation methods involve alloying the aluminum, requiring melting the aluminum at high temperatures, consuming a lot of energy, and posing risks. After the aluminum alloy is formed, the added metals are difficult to remove from the aluminum interior, resulting in lower purity alumina. Furthermore, the activated metals cannot be recycled, leading to high manufacturing costs. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for the direct hydrolysis of activated aluminum using Ga-In melt to prepare α-Al2O3. By using Ga-In melt to activate aluminum, the aluminum can react with water at room temperature and pressure. The hydrolysis product is then calcined to obtain α-Al2O3.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] A method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum in Ga-In melt, the method comprising the following steps:

[0007] (1) Add gallium and indium to a graphite crucible, heat to 170~200℃ to melt, stir evenly and keep warm for more than 20 minutes to obtain Ga-In melt; based on the total mass of gallium and indium as 100%, the mass fraction of gallium is 20%~80%; the mass fraction of indium is 20%~80%. (2) Immerse the aluminum sheet in Ga-In melt for 1~10 min, remove the aluminum sheet to obtain activated aluminum sheet, and store it in a vacuum bag; (3) Mix the activated aluminum sheet with pure water and stir at 20-30 rpm for 12-24 hours to generate hydrolysis products; (4) Dry and grind the hydrolysis product to obtain the ground powder, and seal the ground powder in an aluminum foil bag for storage; (5) Place the ground powder in a corundum crucible, then place the crucible in a tube furnace and calcine at 1200~1300℃ for 1.5~2h to obtain α-Al2O3; (6) Grind α-Al2O3 and then place it in a tube furnace and calcine it at 1500~1550℃ for 1.5~2h. After calcination, high-purity α-Al2O3 is obtained.

[0008] Preferably, in step (1), with the total mass of gallium and indium being 100%, the mass fraction of gallium is 50% to 60% and the mass fraction of indium is 40% to 50%.

[0009] Preferably, in step (1), the heating rate is 5~10℃ / min.

[0010] Preferably, in step (2), the thickness of the aluminum sheet is less than or equal to 1 cm.

[0011] Preferably, in step (3), the mass ratio of aluminum sheet to water is 1:10~12.

[0012] Preferably, in step (5), argon gas is first introduced to raise the temperature to 700±10℃, and after reaching the temperature, the argon gas is stopped, and the temperature is continued to rise to 1200~1300℃ under a vacuum atmosphere.

[0013] Preferably, in step (5), the heating rate is 5~10℃ / min.

[0014] Preferably, in step (6), the calcination atmosphere is a vacuum.

[0015] Preferably, in step (6), the heating rate is 5~10℃ / min.

[0016] A high-purity α-Al₂O₃ was prepared by the above method.

[0017] Beneficial effects This invention uses Ga-In alloy melt to activate aluminum. The activation method is simple and efficient, allowing aluminum to react with water at room temperature and pressure. During hydrolysis, prolonged stirring causes the Ga-In alloy to agglomerate and settle, removing most of the Ga-In metal, which can then be recycled. A secondary calcination process yields high-purity α-Al₂O₃. Compared to alloy smelting activation, this method allows for activation at lower temperatures, is simpler, and takes less time. For the activated aluminum, the Ga-In melt exists only on the surface, making Ga-In metal removal easier and resulting in higher purity α-Al₂O₃. This invention eliminates the need for aluminum alloying; the added metal exists only on the surface and is easily removed, resulting in high-purity alumina. The aluminum activation method is simple and quick, with a short preparation cycle, recyclable activated metal, and low production cost. Attached Figure Description

[0018] Figure 1 The hydrogen production curve is shown in Example 1, which is the reaction curve of aluminum sheet with water.

[0019] Figure 2 The image shows the XRD pattern of the high-purity α-Al2O3 prepared in Example 1.

[0020] Figure 3 This is a SEM image of the high-purity α-Al2O3 prepared in Example 1. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments.

[0022] Example 1 Starting with gallium blocks and indium granules, weigh out 20% gallium and 80% indium by mass percentage. Add the weighed metals to a graphite crucible, and then mount the crucible onto a heating platform. Set the heating platform temperature to 200℃ with a heating rate of 10℃ / min. After the heating platform reaches 200℃, use a stirring rod to stir the Ga-In melt in the graphite crucible until homogeneous, and hold at this temperature for 20 minutes. After holding at this temperature, cut aluminum sheets with a thickness of 1mm, immerse the aluminum sheets in the Ga-In melt for 1 minute, and then remove the aluminum sheets and store them in a vacuum bag.

[0023] At room temperature and pressure, activated aluminum sheets were stirred with pure water for 12 hours to generate hydrolysis products. The mass ratio of aluminum sheets to water was 1:10. After the reaction was complete, the supernatant was collected, and the product was placed in an 80°C oven for 48 hours to allow the moisture in the product to evaporate completely. The dried product was then ground into powder using a mortar and pestle. The ground product was then sealed and stored in an aluminum foil bag.

[0024] The ground product was placed in a corundum crucible, which was then placed in a tube furnace for calcination to prepare α-Al₂O₃. The calcination temperature was 1300℃, the heating rate was 5℃ / min, and the holding time was 2h. The atmosphere was argon below 700℃ and vacuum above 700℃. The prepared α-Al₂O₃ was then ground and subjected to a second calcination in a tube furnace at 1500℃, a heating rate of 5℃ / min, and a holding time of 2h under vacuum. This yielded the high-purity α-Al₂O₃ described in this invention.

[0025] Example 2 Starting with gallium blocks and indium granules, weigh out 60% gallium and 40% indium by mass percentage. Add the weighed metals to a graphite crucible, and then mount the crucible onto a heating platform. Set the heating platform temperature to 200℃ with a heating rate of 10℃ / min. After the heating platform reaches 200℃, use a stirring rod to stir the Ga-In melt in the graphite crucible until homogeneous, and hold at this temperature for 20 minutes. After holding at this temperature, cut aluminum sheets with a thickness of 3mm, immerse the aluminum sheets in the Ga-In melt for 5 minutes, and then remove the aluminum sheets and store them in a vacuum bag.

[0026] At room temperature and pressure, activated aluminum sheets were stirred with pure water for 18 hours to generate a hydrolysis product. The mass ratio of aluminum sheets to water was 1:10. After the reaction was complete, the supernatant was collected, and the product was placed in an 80°C oven for 48 hours to allow the moisture in the product to evaporate completely. The dried product was then ground into powder using a mortar and pestle. The ground product was then sealed and stored in an aluminum foil bag.

[0027] The ground product was placed in a corundum crucible, which was then placed in a tube furnace for calcination to prepare α-Al₂O₃. The calcination temperature was 1300℃, the heating rate was 5℃ / min, and the holding time was 2h. The atmosphere was argon below 700℃ and vacuum above 700℃. The prepared α-Al₂O₃ was then ground and subjected to a second calcination in a tube furnace at 1500℃, a heating rate of 5℃ / min, and a holding time of 2h under vacuum. This yielded the high-purity α-Al₂O₃ described in this invention.

[0028] Example 3 Starting with gallium blocks and indium granules, weigh out 80% gallium and 20% indium by mass percentage. Add the weighed metals to a graphite crucible, and then mount the crucible onto a heating platform. Set the heating platform temperature to 200℃ with a heating rate of 10℃ / min. After the heating platform reaches 200℃, use a stirring rod to stir the Ga-In melt in the graphite crucible until homogeneous, and hold at this temperature for 20 minutes. After holding at this temperature, cut aluminum sheets with a thickness of 8mm, immerse the aluminum sheets in the Ga-In melt for 10 minutes, and then remove the aluminum sheets and store them in a vacuum bag.

[0029] At room temperature and pressure, activated aluminum sheets were stirred with pure water for 24 hours to generate hydrolysis products. The mass ratio of aluminum sheets to water was 1:10. After the reaction was complete, the supernatant was collected, and the product was placed in an 80℃ oven for 48 hours to allow the moisture in the product to evaporate completely. The dried product was then ground into powder using a mortar and pestle. The ground product was then sealed and stored in an aluminum foil bag.

[0030] The ground product was placed in a corundum crucible, which was then placed in a tube furnace for calcination to prepare α-Al₂O₃. The calcination temperature was 1300℃, the heating rate was 5℃ / min, and the holding time was 2h. The atmosphere was argon below 700℃ and vacuum above 700℃. The prepared α-Al₂O₃ was then ground and subjected to a second calcination in a tube furnace at 1500℃, a heating rate of 5℃ / min, and a holding time of 2h under vacuum. This yielded the high-purity α-Al₂O₃ described in this invention.

[0031] Hydrogen production test of aluminum sheet hydrolysis: A certain amount of sample is added to a three-necked flask, and the flask mouth is sealed with a rubber stopper. Then, purified water is injected into the three-necked flask using a syringe. A reaction occurs inside the three-necked flask to produce hydrogen gas. The produced hydrogen gas passes through a condenser and a drying tube in sequence and enters the Qixing Huachuang CS200 gas flow meter. Finally, the hydrogen gas is discharged into the outdoor air by an exhaust fan. A computer is connected to the gas flow meter to record and save the data.

[0032] The hydrogen production performance of the reaction between 0.25g of activated aluminum sheet and 5ml of purified water in Example 1 was tested at room temperature using the above method. The hydrogen production amount and rate of the aluminum sheet are as follows: Figure 1 As shown, activated aluminum sheets can spontaneously react with pure water at room temperature, and the hydrogen production rate exhibits a typical "S"-shaped curve with time. The reaction between the aluminum sheet and water can be divided into three stages: induction, acceleration, and deceleration. During the induction stage, the reaction temperature is low due to insufficient contact between the aluminum sheet and water initially; as the reaction proceeds, the temperature rises slowly, and the reaction rate also increases slowly. During the acceleration stage, after sufficient contact between the aluminum sheet and water, the reaction temperature rises rapidly, and the reaction rate also increases rapidly. During the deceleration stage, after the reaction rate reaches its maximum, the reaction rate gradually decreases until the reaction stops due to the gradually decreasing unreacted aluminum content. The hydrogen production rate and maximum hydrogen production rate of the aluminum sheet can reach 276 ml and 681 ml·min, respectively. -1 ·g -1 .

[0033] X-ray diffraction (XRD) analysis: The hydrolysis products and their phase composition after acid washing and calcination were analyzed using XRD. The X-ray diffractometer used was manufactured by PAN-alytical, Netherlands, and the model was X.pert.PRO.MPD.X. The relevant parameters for the test were as follows: monochromatic CuKα rays (λCuKα = 0.15418 nm), tube voltage of 40 kV, tube current of 30 mA, scan start angle of 10°, end angle of 90°, and scan rate of 8°·min. -1 .

[0034] XRD analysis was performed on the hydrolysis product from Example 1 after calcination treatment, and the results are as follows: Figure 2 As shown. The main product of the aluminum sheet hydrolysis reaction is AlO(OH), therefore the following reaction occurs during the hydrolysis process: Al + 2H₂O → AlOOH + 3 / 2H₂↑. After calcination, the hydrolysis product is completely transformed from AlOOH to α-Al₂O₃.

[0035] Scanning electron microscopy (SEM) analysis: The microstructure and phase structure of high-purity α-Al₂O₃ were observed using a scanning electron microscope (SEM). The SEM used was a Hitachi Instruments Co., Ltd. model FE-SEM-S4800. The relevant parameters during testing were: secondary electron (SE) imaging mode, scanning voltage of 5 kV, and current of 10 μA; when switching to energy dispersive spectroscopy (EDS), the scanning voltage was increased to 15 kV. During sample preparation, the sample was placed on conductive tape and then sputtered with gold.

[0036] The final sample prepared in Example 1 was subjected to SEM testing. The results are as follows: Figure 3 As shown, the morphology of high-purity α-Al2O3 is relatively uniform, exhibiting a dendritic structure with a size of about 5 μm.

[0037] Purity test: According to GB / T 6609.2-2022, GB / T 6609.1-2018, GB / T 6609.34-2009 and GB / T 30902-2014, the contents of Fe2O3, SiO2, CaO, MgO, Na2O, Li2O, MnO, NiO, V2O5, Ga2O3, SnO2, and B2O3, as well as the loss on ignition, were tested. Finally, the purity of the high-purity α-Al2O3 prepared in Example 1 was calculated to be 99.92%.

[0038] The performance test results of Examples 2-3 are similar to those of Example 1.

[0039] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum from Ga-In melt, characterized in that: The method steps include: (1) Add gallium and indium to a graphite crucible, heat to 170~200℃ to melt, stir evenly and keep warm for more than 20 minutes to obtain Ga-In melt; based on the total mass of gallium and indium as 100%, the mass fraction of gallium is 20%~80%; the mass fraction of indium is 20%~80%. (2) Immerse the aluminum sheet in Ga-In melt for 1~10 min, remove the aluminum sheet to obtain activated aluminum sheet, and store it in a vacuum bag; (3) Mix the activated aluminum sheet with pure water and stir at 20-30 rpm for 12-24 hours to generate hydrolysis products; (4) Dry and grind the hydrolysis product to obtain the ground powder, and seal the ground powder in an aluminum foil bag for storage; (5) Place the ground powder in a corundum crucible, then place the crucible in a tube furnace and calcine at 1200~1300℃ for 1.5~2h to obtain α-Al2O3; (6) Grind α-Al2O3 and then place it in a tube furnace and calcine it at 1500~1550℃ for 1.5~2h. After calcination, high-purity α-Al2O3 is obtained.

2. The method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum in Ga-In melt as described in claim 1, characterized in that: In step (1), with the total mass of gallium and indium being 100%, the mass fraction of gallium is 50% to 60% and the mass fraction of indium is 40% to 50%.

3. The method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum in Ga-In melt as described in claim 1, characterized in that: In step (1), the heating rate is 5~10℃ / min.

4. The method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum in Ga-In melt as described in claim 1, characterized in that: In step (2), the thickness of the aluminum sheet is less than or equal to 1 cm.

5. The method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum in Ga-In melt as described in claim 1, characterized in that: In step (3), the mass ratio of aluminum sheet to water is 1:10~12.

6. The method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum in Ga-In melt as described in claim 1, characterized in that: In step (5), argon gas is first introduced to raise the temperature to 700±10℃. After reaching the temperature, the argon gas is stopped, and the temperature is raised to 1200~1300℃ under vacuum.

7. The method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum in Ga-In melt as described in claim 1, characterized in that: In step (5), the heating rate is 5~10℃ / min.

8. The method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum in Ga-In melt as described in claim 1, characterized in that: In step (6), the calcination atmosphere is a vacuum.

9. The method for preparing α-Al₂O₃ by direct hydrolysis of activated aluminum in Ga-In melt as described in claim 1, characterized in that: In step (6), the heating rate is 5~10℃ / min.

10. A high-purity α-Al₂O₃, characterized in that: It is prepared by the method described in any one of claims 1 to 9.

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