Method for preparing alpha-Al2O3 by directly hydrolyzing high-activity aluminum alloy

Abstract

The invention relates to a method for preparing alpha-Al2O3 by directly hydrolyzing a high-activity aluminum alloy, and belongs to the technical field of metal materials. Aluminum is activated, so that the aluminum can react with water at normal temperature and normal pressure, and the conversion rate of the aluminum is close to 100%; the hydrolysis product is subjected to acid pickling treatment, the purity of the hydrolysis product is improved, then the hydrolysis product subjected to acid pickling is subjected to calcination treatment, and finally the high-purity alpha-Al2O3 is obtained. Compared with an alkoxide method, corrosive chemicals are not used, and the preparation process is safer and more environmentally friendly. High temperature and high pressure are not needed, the preparation process is simpler and more efficient, and the preparation cost is reduced.

Description

Technical Field

[0001] The present invention relates to a method for directly hydrolyzing a highly active aluminum alloy to prepare α-Al2O3, belonging to the technical field of metallic materials. Background Art

[0002] High-purity alumina is a versatile inorganic material with extremely wide industrial applications, including the manufacture of advanced ceramics, electronic components, abrasives, cutting materials, refractory materials, optical products, catalyst carriers, biomedical materials, and aerospace components, etc. High-purity alumina is regarded as an important raw material in many industries due to its unique physical and chemical properties, such as high strength, light weight, high temperature resistance, and good optical characteristics.

[0003] The hydrolysis of aluminum isopropoxide, the thermal decomposition of aluminum isopropoxide, and the thermal decomposition of aluminum nitrate can be used for the production of high-purity alumina. Among them, the alcoholate method is a common method for producing alumina. In this process, aluminum isopropoxide is first synthesized by dissolving aluminum in isopropanol. Then, several purification steps are carried out on aluminum isopropoxide to reduce the impurity content, and then hydrolysis is carried out by liquid water or water vapor. Aluminum hydroxide is formed during this process. Further calcination can produce alumina. The alcoholate method uses corrosive chemicals and can cause dangerous pollution.

[0004] The hydrothermal oxidation of aluminum is a promising method for preparing high-purity alumina. In a continuous hydrothermal reactor, hydroxyalumina with a large surface area and microporous structure can be produced at a temperature of about 300 °C and a pressure of about 10 MPa without any additives. During the hydrothermal oxidation process, only aluminum in the form of micron-sized powder and distilled water are used as the initial reagents. The aluminum conversion rate is close to 100%. The hydrothermal oxidation of aluminum cannot convert aluminum into hydroxyalumina at normal temperature and pressure, which will increase the preparation cost and risk. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for directly hydrolyzing a highly active aluminum alloy to prepare α-Al2O3. The aluminum is activated so that it can react with water at normal temperature and pressure. After hydrolysis, the product is calcined to obtain α-Al2O3.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows.

[0007] A method for directly hydrolyzing a highly active aluminum alloy to prepare α-Al2O3, the method steps include:

[0008] (1) Using aluminum as the main raw material, and one or more of gallium, indium, tin, bismuth, and zinc as the auxiliary raw materials. Based on the total mass of the raw materials being 100%, the mass fraction of the main raw material is 95% - 96%, and the mass fraction of the auxiliary raw material is 4% - 5%;

[0009] (2) Add the main raw material and auxiliary raw materials into a graphite crucible, place the graphite crucible in a melting furnace, and under the atmosphere of protective gas, heat the melting furnace to 900 ± 50 °C and keep it warm for more than 30 min to obtain a melt.

[0010] (3) After the heat preservation is completed, pour the melt into a preheated rectangular graphite mold. After cooling, a sheet-like titanium alloy is obtained in the rectangular graphite mold.

[0011] (4) Under normal temperature and pressure, carry out a hydrolysis reaction between the sheet-like aluminum alloy and pure water. After the reaction is completed, dry the hydrolysis product and grind it into powder to obtain a powdered hydrolysis product.

[0012] (5) Wash, dry, and calcine the powdered hydrolysis product to obtain α-Al2O3.

[0013] Preferably, in step (1), among the auxiliary raw materials, gallium accounts for less than 2% of the total mass of the raw materials, and other auxiliary raw materials each account for less than 1% of the total mass of the raw materials.

[0014] Preferably, in step (2), during heat preservation, stir the melt in the furnace once every 5 - 10 min.

[0015] Preferably, in step (3), the preheating temperature of the rectangular graphite mold is 300 - 350 °C, and the heat preservation time is more than 15 min.

[0016] Preferably, in step (3), the thickness of the sheet-like titanium alloy is less than or equal to 2 mm.

[0017] Preferably, in step (4), the mass ratio of the sheet-like aluminum alloy to pure water is 1:10 - 12.

[0018] Preferably, in step (4), the drying temperature is 70 - 90 °C, and the drying time is more than 48 h.

[0019] Preferably, in step (5), add the powdered hydrolysis product into an acetic acid aqueous solution, stir for more than 2 h. After the stirring is completed, carry out suction filtration, and dry the solid at 70 - 90 °C for more than 24 h.

[0020] Preferably, in step (5), during calcination, under the atmosphere of protective gas, keep it warm at 1200 - 1400 °C for 2 - 3 h.

[0021] An α-Al2O3 is prepared by the above method.

[0022] Beneficial effects

[0023] In the present invention, aluminum is activated so that it can react with water at normal temperature and pressure, and the conversion rate of aluminum is close to 100%; the hydrolysis product is pickled to improve the purity of the hydrolysis product, and then the pickled hydrolysis product is calcined to finally obtain high-purity α-Al2O3. Compared with the alcohol salt method, corrosive chemicals are not used, and the preparation process is safer and greener. High temperature and high pressure are not required, the preparation process is simpler and more efficient, and the preparation cost is reduced. Description of the Drawings

[0024] Figure 1 It is the hydrogen production curve of the aluminum alloy sheet reacting with water in Example 1.

[0025] Figure 2 It is the XRD pattern of the hydrolyzed aluminum alloy sheet in Example 1.

[0026] Figure 3 It is the XRD pattern of the product after calcination treatment in Example 1.

[0027] Figure 4 It is the SEM image of the product after calcination treatment in Example 1. Detailed Description of the Invention

[0028] The present invention will be further described in detail below with reference to specific embodiments.

[0029] Example 1

[0030] Taking aluminum pellets, gallium blocks, indium pellets, tin pellets, bismuth pellets, and zinc pellets as starting materials, 95% Al, 2% gallium, 1% indium, 1% tin, and 1% bismuth are weighed according to mass percentage. The weighed metals are added to a graphite crucible, and then the graphite crucible is installed in an M.MF.03000 melting furnace. During the heating process, argon is introduced into the melting furnace to prevent the metals from being oxidized during heating. When the temperature of the melting furnace reaches 900 °C and the metals in the furnace are melted, keep the temperature for 30 min and stir the melt in the furnace every 10 min. After placing a rectangular graphite mold on a WY-01B heating furnace and keeping it at 300 °C for 15 minutes, pour the aluminum alloy melt in the melting furnace into the rectangular graphite, ensuring that the melt height is less than 2 mm. After the aluminum alloy cools slowly, a sheet-shaped aluminum alloy is obtained, and the aluminum alloy is sealed and stored with an aluminum foil bag.

[0031] At normal temperature and pressure, the prepared aluminum alloy sheet reacts with pure water to generate a hydrolysis product, and the mass ratio of the aluminum alloy to water is 1:10. After the reaction is complete, the product is placed in an 80 °C oven for 48 hours to completely volatilize the water in the product. Use a mortar to grind the dried product into powder. Take a certain amount of the product, add a certain amount of acetic acid and pure water, stir and react in a beaker for 2 h. After the reaction is complete, carry out suction filtration treatment, take out the solid and place it in an 80 °C oven for 24 hours, and seal and store the dried product with an aluminum foil bag.

[0032] Place the product after pickling and drying in a corundum crucible, then place the crucible in a tube furnace, and use the tube furnace to calcine the product. The calcination temperature is 1300 °C, the holding time is 2 h, and the atmosphere is argon. The high-purity α-Al2O3 described in the present invention is prepared.

[0033] Hydrogen production test of aluminum alloy hydrolysis

[0034] Add a certain amount of sample to a three-necked flask and seal the flask mouth with a rubber stopper. Then inject pure water into the three-necked flask with a syringe. A reaction occurs in the three-necked flask to produce hydrogen. The produced hydrogen passes through a condenser and a drying tube in sequence and enters a gas flowmeter MF-4000, and finally the hydrogen is discharged into the outdoor air through an exhaust fan. The computer is connected to the gas flowmeter to record and save data.

[0035] The hydrogen production performance of the reaction of 0.19 g of aluminum alloy with 1.9 ml of pure water was tested at room temperature by the above method. The hydrogen production amount and hydrogen production rate of the aluminum alloy are as Figure 1 shown. At room temperature, the aluminum alloy can react spontaneously with pure water, and the relationship between the hydrogen production amount and time shows a typical "S"-shaped curve. The reaction of the aluminum alloy with water is divided into three stages, namely the induction period, the acceleration period and the deceleration period. In the induction period, due to the insufficient contact between the aluminum alloy and water at the initial stage of the reaction and the low reaction temperature, the reaction temperature slowly rises with the progress of the reaction, and the reaction rate also slowly increases; in the acceleration period, after the aluminum alloy is in full contact with water, the reaction temperature rapidly rises, and the reaction rate of the aluminum alloy with water also rapidly increases; in the deceleration period, after the reaction rate reaches the maximum, due to the gradual decrease of the unreacted aluminum content, the reaction rate gradually decreases until the reaction stops. The hydrogen production amount and the maximum hydrogen production rate of the aluminum alloy can reach 226 ml and 530 ml·min -1 ·g -1 , and the conversion rate reaches 100%.

[0036] X-ray diffraction (XRD) analysis

[0037] Use XRD to test and analyze the phase composition of the hydrolysis product and the product after pickling and calcination treatment. The manufacturer of the X-ray diffractometer used is PAN-alytical Company in the Netherlands, and the equipment model is X.pert.PRO.MPD.X. The relevant parameters during the test are: using monochromatic CuKα ray (λCuKα = 0.15418 nm), the tube voltage used for scanning is 40 kV, the tube current is 30 mA, the starting scanning angle is 10°, the ending angle is 90°, and the scanning rate is 8°·min -1 .

[0038] Perform XRD tests on the hydrolysis product and the product after pickling and calcination treatment in Example 1. The results are as Figure 2 andFigure 3 As shown in the figure. The main product of the hydrolysis reaction of aluminum alloy is AlOOH. Therefore, the following reaction occurs during hydrolysis: Al + 2H2O → AlOOH + 3 / 2H2↑. After calcination treatment, the hydrolysis product is completely transformed into α-Al2O3.

[0039] Scanning Electron Microscope (SEM) Analysis

[0040] The scanning electron microscope was used to observe the microscopic morphology and phase structure of the hydrolysis product after pickling and calcination treatment. The manufacturer of the scanning electron microscope used is Hitachi Instrument Equipment Co., Ltd., and the equipment model is FE-SEM-S4800. The relevant parameters during testing are as follows: The secondary electron (SE) imaging mode was adopted, the scanning voltage was 5 kV, the current was 10 μA, and the scanning voltage was changed to 15 kV when switching to the energy spectrometer for work. During sample preparation, after placing the sample on the conductive tape, gold spraying operation is required.

[0041] The sample finally prepared in Example 1 was tested by SEM. The results are as Figure 4 shown. After calcination treatment, the morphology of α-Al2O3 is relatively uniform, showing a dendritic structure with a size of about 5 μm.

[0042] Example 2

[0043] Using aluminum pellets, gallium blocks, indium pellets, tin pellets, bismuth pellets, and zinc pellets as starting materials, 95% Al, 2% gallium, 1% indium, 1% tin, and 1% zinc were weighed according to mass percentage. The weighed metals were added to a graphite crucible, and then the graphite crucible was installed in an M.MF.03000 melting furnace. During heating, argon gas was introduced into the melting furnace to prevent the metals from being oxidized during heating. When the temperature of the melting furnace reached 900 °C and the metals in the furnace were melted, it was kept warm for 30 min and the melt in the furnace was stirred every 10 min. After placing a rectangular graphite mold on a WY-01B heating furnace and keeping it at 300 °C for 15 minutes, the aluminum alloy melt in the melting furnace was poured into the rectangular graphite, ensuring that the melt height was less than 2 mm. After the aluminum alloy was slowly cooled, a sheet-shaped aluminum alloy was obtained, which was sealed and stored in an aluminum foil bag.

[0044] Under normal temperature and pressure, the prepared aluminum alloy sheet was reacted with pure water to generate hydrolysis products, and the mass ratio of aluminum alloy to water was 1:10. After the reaction was complete, the product was placed in an 80 °C oven for 48 hours to completely volatilize the water in the product. The dried product was ground into powder using a mortar. A certain amount of the product was taken, a certain amount of acetic acid and pure water were added, and the mixture was stirred and reacted in a beaker for 2 h. After the reaction was completed, filtration treatment was carried out, and the solid was taken out and placed in an 80 °C oven for 24 hours, and the dried product was sealed and stored in an aluminum foil bag.

[0045] Place the pickled and dried product in a corundum crucible, then place the crucible in a tube furnace, and use the tube furnace to calcine the product. The calcination temperature is 1300 °C, the holding time is 2 h, and the atmosphere is argon. The high-purity α-Al2O3 described in the present invention is prepared.

[0046] The performance test results are similar to those of Example 1.

[0047] Example 3

[0048] Using aluminum pellets, gallium blocks, indium pellets, tin pellets, bismuth pellets, and zinc pellets as starting materials, weigh 96% Al, 2% gallium, 1% indium, and 1% bismuth according to mass percentage. Add the weighed metals to a graphite crucible, and then install the graphite crucible into an M.MF.03000 melting furnace. During the heating process, introduce argon into the melting furnace to prevent the metals from being oxidized during heating. When the temperature of the melting furnace reaches 900 °C and the metals in the furnace are melted, hold for 30 min and stir the melt in the furnace every 10 min. Place a rectangular graphite mold on a WY-01B heating furnace and keep it at 300 °C for 15 minutes, then pour the aluminum alloy melt in the melting furnace into the rectangular graphite, ensuring that the melt height is less than 2 mm. After the aluminum alloy cools slowly, obtain flaky aluminum alloy, and seal and store the aluminum alloy with an aluminum foil bag.

[0049] Under normal temperature and pressure, react the prepared aluminum alloy sheet with pure water to generate hydrolysis products, and the mass ratio of aluminum alloy to water is 1:10. After the reaction is complete, place the product in an 80 °C oven for 48 hours to completely volatilize the water in the product. Use a mortar to grind the dried product into powder. Take a certain amount of the product, add a certain amount of acetic acid and pure water, stir and react in a beaker for 2 h. After the reaction is completed, perform suction filtration, take out the solid and place it in an 80 °C oven for 24 hours, and seal and store the dried product with an aluminum foil bag.

[0050] Place the pickled and dried product in a corundum crucible, then place the crucible in a tube furnace, and use the tube furnace to calcine the product. The calcination temperature is 1300 °C, the holding time is 2 h, and the atmosphere is argon. The high-purity α-Al2O3 described in the present invention is prepared.

[0051] The performance test results are similar to those of Example 1.

[0052] In summary, the invention includes but is not limited to the above embodiments. Any equivalent replacement or partial improvement carried out under the spirit and principle of the present invention will be regarded as within the protection scope of the present invention.

Claims

1. A method for directly hydrolyzing a high-activity aluminum alloy to prepare α-Al2O3, characterized in that: The method steps include: (1) Using aluminum as the main raw material and one or more of gallium, indium, tin, bismuth, and zinc as auxiliary raw materials. Based on the total mass of the raw materials being 100%, the mass fraction of the main raw material is 95% - 96%, and the mass fraction of the auxiliary raw materials is 4% - 5%; (2) Adding the main raw material and the auxiliary raw materials into a graphite crucible, placing the graphite crucible in a melting furnace, heating the melting furnace to 900 ± 50 °C under a protective gas atmosphere, and holding for more than 30 minutes to obtain a melt; (3) After the holding is completed, pouring the melt into a preheated rectangular graphite mold, and after cooling, obtaining a sheet-like titanium alloy in the rectangular graphite mold; (4) Under normal temperature and pressure, carrying out a hydrolysis reaction between the sheet-like aluminum alloy and pure water. After the reaction is completed, drying the hydrolysis product and grinding it into powder to obtain a powdered hydrolysis product; (5) Washing, drying, and calcining the powdered hydrolysis product to obtain α - Al2O3.

2. The method for directly hydrolyzing a highly active aluminum alloy to prepare α-Al2O3 according to claim 1, characterized in that: In step (1), among the auxiliary raw materials, the mass fraction of gallium in the total mass of the raw materials is less than 2%, and the mass fractions of the other auxiliary raw materials are each less than 1% of the total mass of the raw materials.

3. The method for directly hydrolyzing a highly active aluminum alloy to prepare α-Al2O3 according to claim 1, wherein: In step (2), during the holding process, the melt in the furnace is stirred once every 5 - 10 minutes.

4. The method for directly hydrolyzing a high-activity aluminum alloy to prepare α-Al2O3 according to claim 1, characterized in that: In step (3), the preheating temperature of the rectangular graphite mold is 300 - 350 °C, and the holding time is more than 15 minutes.

5. The method for directly hydrolyzing a highly active aluminum alloy to prepare α-Al2O3 according to claim 1, characterized in that: In step (3), the thickness of the sheet-like titanium alloy is less than or equal to 2 mm.

6. The method for directly hydrolyzing a highly active aluminum alloy to prepare α-Al2O3 according to claim 1, characterized in that: In step (4), the mass ratio of the sheet-like aluminum alloy to pure water is 1:10 - 12.

7. The method for directly hydrolyzing a highly active aluminum alloy to prepare α-Al2O3 according to claim 1, characterized in that: In step (4), the drying temperature is 70 - 90 °C, and the drying time is more than 48 hours.

8. A method for directly hydrolyzing a high-activity aluminum alloy to prepare α-Al2O3 as described in claim 1, characterized in that: In step (5), adding the powdered hydrolysis product into an acetic acid aqueous solution, stirring for more than 2 hours. After the stirring is completed, performing suction filtration, and drying the solid at 70 - 90 °C for more than 24 hours.

9. The method for directly hydrolyzing a high-activity aluminum alloy to prepare α-Al2O3 according to claim 1, wherein: In step (5), during calcination, under a protective gas atmosphere, holding at 1200 - 1400 °C for 2 - 3 hours.

10. An α-Al2O3, characterized in that: Prepared by the method according to any one of claims 1 - 9.

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