Low-temperature preparation method of flaky interlocking regular hexagonal alpha-Al2O3 powder

Abstract

The invention discloses a low-temperature preparation method of flaky interlocking regular hexagonal alpha-Al2O3 powder, which is characterized by comprising the following steps: step 1, uniformly mixing and stirring aluminum sec-butoxide or aluminum isopropoxide and n-butyl alcohol, then adding a mineralizing agent, and uniformly stirring to prepare a solution A; 2, mixing deionized water, acetonitrile and n-butyl alcohol to prepare a solution B; 3, slowly dropwise adding the solution B into the solution A prepared in the step 1 to obtain a milk white floccule, and filtering, drying, grinding and sieving to obtain precursor powder; and step 4, calcining the precursor powder to prepare the alpha-Al2O3 powder with the flaky interlocking regular hexagonal morphology. According to the invention, the problems of difficult preparation, complex process and high energy consumption of flaky alumina are solved, the operation is simple, large-scale production is facilitated, and the prepared product can be applied to the fields of low-temperature sintered ceramics, pigments, cosmetics, automotive finish, toughened ceramics and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic powder synthesis, and particularly relates to a low-temperature preparation method of flaky interlocked regular hexagonal α-Al2O3 powder. Background Art

[0002] Due to its physical and chemical properties, alumina has a wide range of applications in the fields of electronics, ceramics, catalysts, etc. However, the phase transition temperature for the reaction of transition-phase alumina to form α-Al2O3 crystals is above 1200°C. At this time, solid-state mass transfer mainly plays a role. Although traditional high-temperature sintering methods can prepare alumina, they have problems such as high energy consumption and high cost. With the increasing requirements for environmental protection and energy efficiency, it has become particularly important to develop low-temperature and low-cost alumina preparation technologies.

[0003] Flaky alumina has excellent comprehensive properties, such as high melting point, high hardness, high mechanical strength, good wear resistance, chemical erosion resistance, oxidation resistance, and good heat resistance. The size of flaky alumina is in the micron range, the thickness of the flakes is in the nanometer range, and the aspect ratio is large, having the dual effects of both nano and micron. The surface activity is moderate, which can not only effectively combine with other active groups, but also is not easy to agglomerate and is convenient for effective dispersion. It can be applied to fields such as pigments, cosmetics, automotive topcoats, coatings, refractory materials, and toughened ceramics. Currently, the preparation methods of flaky alumina include gel method, molten salt method, explosion method, and hydrothermal method, etc.

[0004] For example, Chinese Patent CN103013443B discloses a method for preparing α-Al2O3-based abrasives containing flaky structures. The abrasive particles prepared by this invention contain flaky structures and have the characteristics of good self-sharpening and long durability. However, the preparation process using the sol-gel method is relatively complex, environmentally unfriendly, and has a high preparation cost. CN114958035A reacts an aluminum salt aqueous solution with an alkali solution to obtain a colloid, calcines it at 550 °C to obtain γ-aluminum oxide, mixes it with molten salt and grinds it, and finally calcines it to obtain flaky alumina. WO2008 / 026829 A1, US10647861 B2, US11479681B2, etc. use aluminum sulfate as the main aluminum source, react by adding an aqueous sodium carbonate solution, and add some morphology regulators during the reaction to obtain a colloid, and calcine the dried solution to obtain flaky alumina. In this process, the preparation of the precursor is troublesome, the process is long, resulting in high energy consumption and large losses. Chinese Patent CN104724743A discloses a method for preparing flaky nano-α-Al2O3. Mix aluminum hydroxide and cyclotrimethylene trinitramine evenly, put them into a spherical explosion container, detonate with an electric detonator, and collect the powdery product after detonation to obtain flaky nano-α-Al2O3. Although this method is simple and economical, the danger of detonator detonation is too high, and the formed flaky structure is uneven, and the flaky product yield is low. Chinese Patent CN103241753B discloses a method for preparing α-Al2O3. By using ammonium nitrate or ammonium chloride as a mineralizer, mixing it with a hydrated alumina raw material, and calcining and cooling, α-Al2O3 with a uniform particle size distribution and a large specific surface area is obtained. The alumina formed by this method is prone to agglomeration, and a product with fine particles, light agglomeration degree, and good dispersibility cannot be obtained. Therefore, it is necessary to develop a method that is simple in process and low in cost while ensuring the controllable morphology of flaky alumina to make up for the utilization limitations of flaky alumina due to high costs and energy consumption. Summary of the Invention

[0005] In order to overcome the problems of the prior art, the present invention provides a low-temperature preparation method for flaky interlocked regular hexagonal α-Al2O3 powder with low cost, simple process, and suitable for large-scale production.

[0006] The technical solution of the present invention is: a low-temperature preparation method for flaky interlocked regular hexagonal α-Al2O3 powder, which is characterized by including the following steps: Step 1: Mix aluminum sec-butoxide or aluminum isopropoxide with n-butanol and stir evenly, then add a mineralizer and stir evenly to prepare solution A; Step 2: Mix deionized water, acetonitrile, and n-butanol to prepare solution B; Step 3: Slowly drop the solution B prepared in Step 2 into the solution A prepared in Step 1 to obtain a milky white floc, and then obtain the precursor powder through filtration, drying, grinding, and sieving processes; Step 4: Calcinate the precursor powder obtained in Step 3 to prepare α-Al2O3 powder with a flaky interlocked regular hexagon morphology; The mineralizer in Step 1 is one of aluminum fluoride, potassium fluoride, and sodium fluoride; The molar ratio of aluminum sec-butoxide or aluminum isopropoxide, mineralizer, and n-butanol in Step 1 is 1: 0.1 - 0.6: 0.25 - 0.75; The molar ratio of deionized water, acetonitrile, n-butanol to aluminum sec-butoxide or aluminum isopropoxide in Step 2 is 2 - 4: 3 - 5: 0.25 - 1.25: 1; The calcination temperature in Step 4 is 950 - 1200 °C, the heat preservation time is 0.5 - 1.5 h, and the heating rate is 3 - 5 °C / min.

[0007] The drying process in Step 3 is to keep warm in an oven at 80 - 100 °C for 6 - 12 h.

[0008] The grinding process in Step 3 is to place the dried product in a mortar and grind it.

[0009] The sieving process in Step 3 is to pass through a 200 - 325 mesh sieve.

[0010] The thickness of the α-Al2O3 powder with a flaky interlocked regular hexagon morphology in Step 4 is 100 - 300 nm, the diameter is 1 - 3 μm, and it has a flaky interlocked micro-nano structure formed by assembling regular hexagon structures.

[0011] To ensure the uniformity and controllability of the morphology, the present invention controls the hydrolysis and polycondensation rates of aluminum sec-butoxide through acetonitrile and n-butanol, uses water, highly polar n-butanol, and acetonitrile organic solvents to form a soft template as a protective layer, selects fluoride as the mineralizer, and uses the oxidation and adsorption of F element on the (0001) plane to reduce the surface energy of the (0001) crystal plane. The driving force required to newly generate the (0001) plane with the same area is smaller than that of the (1010) plane. Therefore, the growth of α-Al2O3 crystals is anisotropic, resulting in a significantly faster expansion rate of the (0001) crystal plane. Thus, the alumina particles tend to form regular flaky structures, and α-Al2O3 powder with a flaky interlocked hexagon morphology is prepared.

[0012] The present invention has the following beneficial effects: The operation of the present invention is simple, which is conducive to large-scale production. It can not only reduce the transformation of transitional phase Al2O3 to α-Al2O3, but also the prepared α-Al2O3 powder has no impurities and regular morphology. It is a hexagonal structure without impurity phases, and the morphology presents an interlocked shape assembled by hexagons. It can reach the nanoscale in the thickness direction and the micron scale in the radial direction, with the dual effects of both nano and micron, solving the problems of difficult preparation, complex process and high energy consumption of flaky alumina. The product prepared by the present invention can be applied to fields such as low-temperature sintered alumina ceramics, pigments, cosmetics, automotive topcoats, toughened ceramics, etc. Description of the Drawings

[0013] Figure 1 It is the SEM morphology diagram of the particles prepared in Example 1 of the present invention; Figure 2 It is the TEM morphology diagram of the particles prepared in Example 1 of the present invention; Figure 3 It is the particle size distribution diagram of the particles prepared in Example 1 of the present invention; Figure 4 It is the XRD diagram of the sample prepared in Example 4 of the present invention. Detailed Embodiments

[0014] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0015] Example 1

[0016] Step 1: Dissolve aluminum sec-butoxide in n-butanol and stir to mix evenly, then add mineralizer aluminum fluoride and stir evenly to obtain solution A, where the molar ratio of aluminum sec-butoxide: aluminum fluoride: n-butanol is 1:0.1:0.75.

[0017] Step 2: Mix deionized water, n-butanol and acetonitrile and stir evenly to obtain solution B. The molar ratio of deionized water, acetonitrile, n-butanol to aluminum sec-butoxide in Step 1 is 2:3:0.25:1.

[0018] Step 3: After preparing solutions A and B according to the above Steps 1 and 2, slowly add solution B to solution A and stir evenly to obtain a milky white flocculent substance.

[0019] Step 4: Filter, dry, grind and sieve the milky white flocculent substance obtained in Step 3 to obtain a precursor powder. The drying condition is to keep it warm in an oven at 80°C for 6 h, and grind the powder to pass through a 200-mesh sieve.

[0020] Step 5: Calcinate the precursor powder obtained in Step 4 at 1150°C for 0.5 h with a heating rate of 5°C / min to prepare α-Al2O3 powder.

[0021] Example 2

[0022] Step 1: Dissolve aluminum sec-butoxide in n-butanol and stir to mix evenly. Then add the mineralizer sodium fluoride and stir evenly to obtain Solution A. The molar ratio of aluminum sec-butoxide:sodium fluoride:n-butanol is 1:0.2:0.5.

[0023] Step 2: Mix deionized water, n-butanol, and acetonitrile and stir evenly to obtain Solution B. The molar ratio of deionized water, acetonitrile, n-butanol to aluminum sec-butoxide in Step 1 is 4:4:0.5:1.

[0024] Step 3: After preparing Solutions A and B according to the above Steps 1 and 2 respectively, slowly add Solution B to Solution A and stir evenly to obtain a milky white flocculent substance.

[0025] Step 4: Filter, dry, grind, and sieve the milky white flocculent substance obtained in Step 3 to obtain the precursor powder. The drying condition is to keep warm in an oven at 90 °C for 10 h, and grind the powder to pass through a 250-mesh sieve.

[0026] Step 5: Calcinate the precursor powder obtained in Step 4 at 950 °C for 1.5 h with a heating rate of 3 °C / min to prepare α-Al2O3 powder.

[0027] Example 3

[0028] Step 1: Dissolve aluminum sec-butoxide in n-butanol and stir to mix evenly. Then add the mineralizer potassium fluoride and stir evenly to obtain Solution A. The molar ratio of aluminum sec-butoxide:potassium fluoride:n-butanol is 1:0.5:0.3.

[0029] Step 2: Mix deionized water, n-butanol, and acetonitrile and stir evenly to obtain Solution B. The molar ratio of deionized water, acetonitrile, n-butanol to aluminum sec-butoxide in Step 1 is 4:5:1:1.

[0030] Step 3: After preparing Solutions A and B according to the above Steps 1 and 2 respectively, slowly add Solution B to Solution A and stir evenly to obtain a milky white flocculent substance.

[0031] Step 4: Filter, dry, grind, and sieve the milky white flocculent substance obtained in Step 3 to obtain the precursor powder. The drying condition is to keep warm in an oven at 100 °C for 6 h, and grind the powder to pass through a 325-mesh sieve.

[0032] Step 5: Calcinate the precursor powder obtained in Step 4 at 1200 °C for 0.5 h with a heating rate of 5 °C / min to prepare α-Al2O3 powder.

[0033] Example 4

[0034] Step 1: Dissolve aluminum isopropoxide in n-butanol and stir to mix evenly, then add aluminum fluoride and stir evenly to obtain solution A. The molar ratio of aluminum isopropoxide:aluminum fluoride:n-butanol is 1:0.6:0.25.

[0035] Step 2: Mix deionized water, n-butanol, and acetonitrile and stir evenly to obtain solution B. The molar ratio of deionized water, acetonitrile, n-butanol to aluminum isopropoxide in Step 1 is 3:5:1.25:1.

[0036] Step 3: After preparing solutions A and B according to the above Steps 1 and 2 respectively, slowly add solution B to solution A and stir evenly to obtain a milky white flocculent substance.

[0037] Step 4: Filter, dry, grind, and sieve the milky white flocculent substance obtained in Step 3 to obtain a precursor powder. The drying condition is to keep warm in an oven at 80°C for 12 h, and the powder is ground to pass through a 250-mesh sieve.

[0038] Step 5: Calcinate the precursor powder obtained in Step 4 at 950°C for 1 h with a heating rate of 4°C / min to prepare α-Al2O3 powder.

[0039] As Figure 1 shown, the alumina particles prepared in the embodiment of the present invention generally present a DNA-like structure formed by hexagonal interlocking with a thickness of about 100 - 300 nm and a radial dimension of about 1 - 3 μm under a scanning electron microscope. The monomer hexagon can reach the nanoscale in the thickness direction and the micron scale in the radial dimension, having the dual effects of both nano and micron.

[0040] As Figure 2 shown, the alumina particles prepared in the embodiment of the present invention present a hexagonal morphology with a radial dimension of about 1 - 3 μm under a transmission electron microscope.

[0041] As Figure 3 shown, under the test of a laser particle size analyzer, the alumina powder prepared in the embodiment of the present invention has a relatively wide particle size distribution range and a relatively uniform particle size distribution, among which the proportion of 3 μm is the highest.

[0042] As Figure 4 shown, in the XRD test of the alumina powder prepared in the embodiment of the present invention: the crystal form of the prepared sample is pure α-Al2O3 at 950°C, which is consistent with the standard card (PDF#89 - 7716), indicating that pure α-Al2O3 can be obtained in a relatively wide temperature range.

[0043] The above embodiments merely illustrate the principles and effects of the present invention and some of the applied embodiments, rather than limiting the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention.

Claims

1. A low-temperature preparation method of sheet-like interlocked regular hexagonal α-Al2O3 powder, characterized in that It includes the following steps: Step 1: Mix aluminum sec-butoxide or aluminum isopropoxide with n-butanol and stir evenly, then add a mineralizer and stir evenly to prepare Solution A; Step 2: Mix deionized water, acetonitrile and n-butanol to prepare Solution B; Step 3: Slowly add the Solution B prepared in Step 2 to the Solution A prepared in Step 1 to obtain a milky white flocculent substance, and then obtain the precursor powder through filtration, drying, grinding and sieving processes; Step 4: Calcinate the precursor powder prepared in Step 3 to prepare α-Al2O3 powder with a flaky interlocked regular hexagon morphology; The mineralizer in Step 1 is one of aluminum fluoride, potassium fluoride and sodium fluoride; The molar ratio of aluminum sec-butoxide or aluminum isopropoxide, mineralizer and n-butanol in Step 1 is 1: 0.1-0.6: 0.25-0.75; The molar ratio of deionized water, acetonitrile, n-butanol to aluminum sec-butoxide or aluminum isopropoxide in Step 1 in Step 2 is 2-4: 3-5: 0.25-1.25: 1; The calcination temperature in Step 4 is 950-1200 °C, the heat preservation time is 0.5-1.5 h, and the heating rate is 3-5 °C / min.

2. The low-temperature preparation method according to claim 1, characterized in that: The drying process in Step 3 is to keep warm in an oven at 80-100 °C for 6-12 h.

3. The low-temperature preparation method according to claim 1, characterized in that: The grinding process in Step 3 is to grind the dried product in a mortar.

4. The low-temperature preparation method according to claim 1, characterized in that: The sieving process in Step 3 is to pass through a 200-325 mesh sieve.

5. The low-temperature preparation method according to claim 1, characterized in that: The thickness of the α-Al2O3 powder with a flaky interlocked regular hexagon morphology in Step 4 is 100-300 nm, the diameter is 1-3 μm, and it has a flaky interlocked micro-nano structure formed by assembling regular hexagon structures.

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