High-purity rod-shaped hafnium boride powder and preparation method thereof

Abstract

This invention belongs to the field of hafnium boride powder preparation, specifically disclosing a method for preparing high-purity rod-shaped hafnium boride powder and its preparation via a dual-precursor assisted mechanical synthesis. The preparation method includes: mixing sodium tetraborate, sorbitol, and deionized water to obtain a mixed solution; performing a solvothermal treatment at 60-80℃ for 24-48 hours to obtain a gel; drying and crushing the gel to obtain boron-carbon precursor powder; mixing acetylacetone, hafnium chloride, and anhydrous ethanol under water bath conditions and stirring until homogeneous to obtain a mixed solution; drying and crushing the solution to obtain hafnium precursor powder; thoroughly grinding and mixing the two precursor powders; placing the obtained mixed powder in a tube furnace and introducing a protective gas into the furnace, calcining at 1500-1700℃ for 120-180 minutes to obtain high-purity, rod-shaped hafnium boride powder. The preparation process of this invention is simple, has high production efficiency, and low energy consumption, making it suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of hafnium boride powder preparation technology, and more particularly to a high-purity rod-shaped hafnium boride powder and a preparation method using a dual-precursor assisted mechanical synthesis method. Background Technology

[0002] With the development of technologies such as aerospace, aviation, and atomic energy, the performance of materials used in ultra-high temperature environments needs to be continuously improved in order to adapt to harsh operating conditions.

[0003] Hafnium boride ultra-high temperature ceramics possess high melting point, high hardness, high thermal conductivity, and good thermal shock resistance and chemical stability, thus finding wide application in rocket engines, supersonic vehicles, refractory materials, and nuclear control materials. The synthesis of hafnium boride powder is fundamental to the fabrication of hafnium boride ultra-high temperature ceramic devices, and the powder quality directly affects the device's performance. Currently, industrially prepared hafnium boride powder is predominantly spherical particles; however, hafnium boride ceramics sintered using only spherical particles exhibit high brittleness, failing to meet practical application requirements. Therefore, the development of hafnium boride with high fracture toughness would be of significant importance. Summary of the Invention

[0004] To address the aforementioned shortcomings in the existing technology, one objective of this invention is to provide a method for preparing high-purity rod-shaped hafnium boride powder through dual precursor-assisted mechanical synthesis. This method not only produces high-purity rod-shaped hafnium boride powder with high fracture toughness, but also features a simple process, high production efficiency, and low energy consumption, making it suitable for industrial production.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing high-purity rod-shaped hafnium boride powder, employing a dual-precursor assisted mechanical synthesis method, specifically including the following steps:

[0006] Step A: Under water bath conditions, sodium tetraborate, sorbitol and deionized water are mixed and stirred evenly to obtain mixture 1; mixture 1 is subjected to solvothermal treatment at 60-80℃ for 24-48h to obtain gel; the gel is dried and crushed to obtain boron-carbon precursor powder.

[0007] Step B: Under water bath conditions, acetylacetone, hafnium chloride and anhydrous ethanol are mixed and stirred evenly to obtain mixture 2; mixture 2 is dried and crushed to obtain hafnium precursor powder.

[0008] Step C: Thoroughly mix the boron-carbon precursor powder and the hafnium precursor powder, wherein the molar ratio of sorbitol used in step A to hafnium chloride used in step B is (2-3):1, to obtain a mixed powder; place the mixed powder in a tube furnace and introduce protective gas into the tube furnace, and calcine at 1400-1700℃ for 60-180 min to obtain rod-shaped hafnium boride powder.

[0009] Further improvements to the preparation method of high-purity rod-shaped hafnium boride powder:

[0010] Preferably, the concentration of sodium tetraborate in mixture 1 is 0.38-0.5 mol / L, and the concentration of sorbitol in mixture 1 is 0.16-0.25 mol / L.

[0011] Preferably, the concentration of acetylacetone in mixture 2 is 1.6-3.4 mol / L, and the concentration of hafnium chloride in mixture 2 is 0.4-0.29 mol / L.

[0012] Preferably, the temperature of the water bath in step A is 60-90℃; and the temperature of the water bath in step B is 60-75℃.

[0013] Preferably, in step A, the stirring speed for preparing mixture 1 is 100-600 rpm, and the stirring time is 20-120 min.

[0014] Preferably, in step B, the stirring speed for preparing mixture 2 is 200-450 rpm, and the stirring time is 120-300 min.

[0015] Preferably, the crushing method in steps A and B is ball milling, with a ball milling speed of 50-500 rpm and a ball milling time of 30-120 min.

[0016] Preferably, the gas flow rate of the protective gas in step C is 0.005-50 L / min, the calcination temperature is 1500-1600℃, and the calcination time is 120-180 min.

[0017] A second objective of this invention is to provide a high-purity rod-shaped hafnium boride powder prepared by any of the above-described preparation methods.

[0018] The advantages of this invention compared to the prior art are as follows:

[0019] 1) This invention employs a precursor-assisted mechanosynthesis-carbothermic reduction method to prepare rod-shaped hafnium boride powder with a high aspect ratio. Using acetylacetone, sorbitol, hafnium chloride, and sodium tetraborate as raw materials, the hafnium source is modified by chelating hafnium chloride with acetylacetone, forming a hafnium gel in an ethanol system. Sorbitol and sodium tetraborate form a boron-carbon gel in a deionized water system. After gelling both gels separately, they are ground into powder and uniformly mixed. Organic impurities are removed by calcination, followed by calcination in a high-temperature tube furnace, thus obtaining rod-shaped hafnium boride powder with a high aspect ratio. This preparation method requires only common laboratory equipment, without the need for specialized equipment. The process is simple and easy to control, with a short production cycle. It can be mass-produced and is highly suitable for the large-scale production of related ceramic materials.

[0020] 2) Compared to conventional mechanical mixing methods, the molecular-level mixing of hafnium and boron-carbon precursors, along with the introduction of molten sodium salt, improves the uniformity of the reaction, compensating for the shortcomings of mechanically synthesized powders. Furthermore, the calcination temperature is ensured to be above the melting point of the sodium salt, and the longer holding time removes sodium impurities from the precursors. Therefore, the hafnium boride ceramic powder prepared by this method has high purity and can be used directly. No impurity peaks are shown in the XRD pattern, eliminating the need for further impurity removal. It also exhibits a uniform and excellent microstructure.

[0021] 3) Existing boride ceramic powders are often granular or flake-shaped, requiring toughening to improve their mechanical properties. The hafnium boride powder of this invention can further optimize and enhance its mechanical properties, including compressive strength, shear strength, bending strength, torsional properties, buckling properties, and impact resistance, while maintaining its original thermal protection performance. Therefore, hafnium boride ultra-high temperature ceramics and their composites obtained by sintering this hafnium boride powder with a micro-nano-scale topology will undoubtedly exhibit superior impact resistance, bending resistance, and other mechanical properties while maintaining its excellent thermal protection performance; making them suitable for aerospace vehicles operating in complex environments.

[0022] 4) Existing technologies for preparing rod-shaped hafnium boride powder use n-propanol hafnium as the hafnium source, which is expensive, costing 2-3 times more than hafnium chloride. The present invention provides a dual-precursor assisted mechanical synthesis method for preparing high-purity rod-shaped hafnium boride powder. A sol is prepared using sodium tetraborate, sorbitol, deionized water, acetylacetone, anhydrous ethanol, and hafnium chloride as raw materials. The two dry gel powder precursors, boron-carbon source and hafnium source, are thoroughly mixed, and then calcined at 1400-1700℃ for 60-180 min. This process yields high-purity rod-shaped hafnium boride powder with excellent sintering properties. Furthermore, the process is simple, efficient, and energy-saving, making it suitable for industrial production. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The X-ray diffraction patterns of hafnium boride powder prepared in Examples 1, 1, 2 and 3 of this invention are shown.

[0025] Figure 2 , Figure 3 , Figure 4The images are scanning electron microscope (SEM) images of hafnium boride powder prepared in Example 1 of this invention, at magnifications of 2200, 400, and 8000, respectively.

[0026] Figure 5 , Figure 6 The images shown are scanning electron microscope (SEM) images of hafnium boride powder prepared in Comparative Example 1 of this invention, at magnifications of 900 and 4000.

[0027] Figure 7 , Figure 8 The images shown are scanning electron microscope (SEM) images of hafnium boride powder prepared in Comparative Example 2 of this invention, at magnifications of 1800 and 2000, respectively.

[0028] Figure 9 This is a scanning electron microscope (SEM) image of hafnium boride powder prepared in Comparative Example 3 of the present invention, magnified to 7000.

[0029] Figure 10 This is a scanning electron microscope (SEM) image of hafnium boride powder prepared in Comparative Example 4 of this invention, magnified to 5000.

[0030] Figure 11 Optical images (1) of a bulk hafnium boride obtained by grinding the spherical hafnium boride powder prepared in Comparative Example 3 of the present invention and doping it with the rod-shaped hafnium boride powder prepared in Comparative Example 4, and sintering it, are shown below. Optical images (2) of the bulk hafnium boride obtained by grinding and sintering the powder in Comparative Example 3 of the present invention are shown below. The magnification of the scanning electron microscope images is 5000.

[0031] Figure 12 The images show the fracture toughness of hafnium boride bulk material prepared by grinding spherical hafnium boride powder prepared in Comparative Example 3 and doping it with rod-shaped hafnium boride powder prepared in Comparative Example 4, and the fracture toughness of hafnium boride bulk material prepared by grinding and sintering powder in Comparative Example 3. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0033] The method for preparing high-purity hafnium boride nanorods using a dual-precursor assisted mechanical synthesis method provided by this invention will be described in detail below. Contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art.

[0034] Example 1

[0035] This embodiment provides a method for preparing high-purity rod-shaped hafnium boride powder using a dual-precursor assisted mechanical synthesis method, specifically including the following steps:

[0036] Step A: Under 70℃ water bath conditions, add 15mL of deionized water to a mixture of 3.81g sodium tetraborate and 0.90g sorbitol, and stir to dissolve, thereby obtaining mixture 1; perform solvothermal treatment of mixture 1 in an oven at 60℃ for 24h to obtain a gel; dry the gel at 120℃, and then ball mill it at 200rpm for 60min using a planetary ball mill to obtain boron-carbon precursor powder;

[0037] Step B: Under 70℃ water bath conditions, add 20mL of ethanol to a mixture of 3.20g hafnium chloride and 12g acetylacetone, and stir continuously for 5h to obtain mixture 2; dry mixture 2 in an oven at 100℃, and then ball mill it at 200rpm for 60min using a planetary ball mill to obtain hafnium precursor powder.

[0038] Step C: The boron-carbon precursor powder and hafnium precursor powder are uniformly ground and mixed. The resulting mixed powder is placed in a tube furnace, and argon gas is introduced into the tube furnace as a protective gas. The argon gas flow rate is 2L / min, and the mixture is calcined at 1550℃ for 180min to obtain rod-shaped hafnium boride powder.

[0039] Comparative Example 1

[0040] This comparative example provides a method for preparing high-purity rod-shaped hafnium boride powder using a dual-precursor assisted mechanical synthesis method, comprising the following steps:

[0041] Step A: Under 70℃ water bath conditions, add 20mL of ethanol to a mixture of 3.20g hafnium chloride and 12g acetylacetone, and stir continuously for 5h to obtain a mixture. Dry the mixture in an oven at 100℃, and then ball mill it at 200rpm for 60min using a planetary ball mill to obtain hafnium precursor powder.

[0042] Step B: Grind the hafnium precursor powder with 3.81g of sodium tetraborate powder and mix them evenly. Place the resulting mixed powder in a tube furnace and introduce argon gas into the tube furnace as a protective gas. The argon gas flow rate is 2L / min. Calcine at 1550℃ for 180min to obtain hafnium boride powder.

[0043] Comparative Example 2

[0044] This comparative example provides a method for preparing high-purity rod-shaped hafnium boride powder using a dual-precursor assisted mechanical synthesis method, comprising the following steps:

[0045] Step A: Under 70℃ water bath conditions, add 15mL of deionized water to a mixture of 3.81g sodium tetraborate and 1.21g sorbitol, and stir to dissolve, thus obtaining mixture 1. Place mixture 1 in a 60℃ oven for heat treatment for 24h to obtain a gel; dry the gel at 120℃, and then ball mill it at 200rpm for 60min using a planetary ball mill to obtain boron-carbon precursor powder.

[0046] Step B1: Under 70℃ water bath conditions, 20mL of ethanol was added to a mixture of 3.20g hafnium chloride and 12g acetylacetone, and the mixture was stirred continuously for 5h to obtain mixture 2. Mixture 2 was dried in an oven at 100℃, and then ball-milled at 200rpm for 60min using a planetary ball mill to obtain hafnium precursor powder.

[0047] Step C1: The boron-carbon precursor powder and hafnium precursor powder are uniformly ground and mixed. The resulting mixed powder is placed in a tube furnace, and argon gas is introduced into the tube furnace as a protective gas. The argon gas flow rate is 2L / min. The mixture is calcined at 1550℃ for 180min to obtain partially rod-shaped hafnium boride powder.

[0048] Comparative Example 3

[0049] This comparative example provides a method for preparing high-purity spherical hafnium boride, comprising the following steps:

[0050] Step A: Under a water bath at 60°C, add 20 mL of acetic acid to a mixture of 2.47 g boric acid and 3.03 g sorbitol, stir to dissolve, and then stir evenly to obtain mixture 1.

[0051] Step B: At room temperature, add 20 mL of acetic acid to 3.20 g of hafnium tetrachloride and stir to dissolve. Then stir evenly to obtain mixture 2.

[0052] Step C: Cool mixture 1 to room temperature, then add mixture 2 dropwise to the mixture at a rate of 1-10 mL / min and continue stirring for 30 min to obtain a white suspension.

[0053] Step D: Dry the suspension obtained in step C in an oven at 120°C, and then ball mill it at 200 rpm for 60 minutes to obtain a dry gel powder.

[0054] Step E: Place the dry gel powder obtained in step D into a tube furnace and introduce argon gas into the tube furnace as a protective gas. The argon gas flow rate is 2L / min. Calcinate at 1550℃ for 180min to obtain hafnium boride powder.

[0055] Comparative Example 4

[0056] This comparative example provides a method for preparing high-purity rod-shaped hafnium boride powder, comprising the following steps:

[0057] Step A: Under a water bath at 60°C, add 20 mL of acetic acid to a mixture of 2.47 g boric acid and 3.03 g sorbitol, stir to dissolve, and then stir evenly to obtain a mixed solution.

[0058] Step B: Cool the mixture obtained in Step A to room temperature, then add 7.9 g of hafnium propoxide dropwise to the mixture at a rate of 1-10 mL / min, and continue stirring for 30 min to obtain an orange sol.

[0059] Step C: Dry the sol obtained in step B in an oven at 120°C, and then ball mill it at 200 rpm for 60 minutes to obtain a dry gel powder.

[0060] Step D: Place the dry gel powder obtained in step C into a tube furnace and introduce argon gas into the tube furnace as a protective gas. The argon gas flow rate is 2L / min. Calcinate at 1550℃ for 180min to obtain hafnium boride powder.

[0061] Morphology and purity testing

[0062] (1) The hafnium boride powders prepared in Example 1 and Comparative Examples 1, 2, and 3 of this invention were subjected to material analysis using an X-ray diffraction analyzer, thereby obtaining the following results: Figure 1 The X-ray diffraction pattern shown is from... Figure 1 It can be seen that: Example 1, Comparative Examples 2 and 3 of the present invention have all successfully prepared hafnium boride powder with high purity. Comparative Example 1, due to the lack of sorbitol, resulted in insufficient carbon source, and the prepared hafnium boride powder contained some hafnium oxide.

[0063] (2) The hafnium boride powders prepared in Example 1 and Comparative Examples 1, 2, and 3 of this invention were observed using a scanning electron microscope to obtain the following results: Figure 2-9 The scanning electron microscope image shown. Figure 2-4 These are scanning electron microscope (SEM) images of hafnium boride powder prepared in Example 1 of this invention, at magnifications of 2200, 400, and 8000, respectively; Figure 2-4 It can be seen that the prepared hafnium boride is all rod-shaped grains with uniform morphology, and has a rod-shaped structure of about 5 μm in length and 0.5 μm in thickness. Figure 5 , Figure 6 These are scanning electron microscope (SEM) images of hafnium boride powder prepared in Comparative Example 1 of this invention, at magnifications of 900 and 4000, respectively; Figure 5-6As can be seen, most hafnium boride has a rod-shaped structure, but due to insufficient carbon source, a large amount of hafnium oxide and boron oxide impurities are produced, which appear as large spherical particles in the scan. Figure 7 , Figure 8 These are scanning electron microscope (SEM) images of hafnium boride powder prepared in Comparative Example 2 of this invention, at magnifications of 1800 and 2000, respectively; Figure 7-8 It can be seen that the addition of carbon impurities inhibits the growth of hafnium boride grains; some hafnium boride is rod-shaped, while some hafnium boride is irregularly granular. Figure 9 This is a scanning electron microscope (SEM) image of hafnium boride powder prepared in Comparative Example 3 of this invention, magnified to 7000. Figure 9 It can be seen that the hafnium boride particles are spherical in shape.

[0064] Bulk sintering and performance testing

[0065] The spherical hafnium boride powder prepared in Comparative Example 3 was milled at 2400 rpm for 1 h, and then doped with the rod-shaped hafnium boride powder prepared in Comparative Example 4. The doping amount of the rod-shaped hafnium boride was 10%, and the mixture was sintered at 1800 °C for 0.2 h to obtain hafnium boride bulk 1. The spherical hafnium boride powder prepared in Comparative Example 3 was milled at 2400 rpm for 1 h, and the resulting powder was sintered at 1800 °C for 0.2 h to obtain hafnium boride bulk 2. The scanning electron microscope image of hafnium boride bulk 1 is shown below. Figure 11 As shown in (1), the scanning electron microscope image of hafnium boride bulk 2 is as follows. Figure 11 (2) is shown. The fracture toughness of hafnium boride blocks 1 and 2 was tested, and the results are shown in Figure 1. Figure 12 As shown, the values ​​are 5.88 MPa·m 1 / 2 3.85 MPa·m 1 / 2 The results showed that doping with 10% rod-shaped hafnium boride powder improved the fracture toughness of the sintered hafnium boride bulk by about 53%.

[0066] In summary, rod-shaped hafnium boride can indeed improve the fracture toughness of hafnium boride ceramics. Furthermore, the embodiments of this invention can not only produce high-purity rod-shaped hafnium boride powder, but also have a simple process, high production efficiency, and low energy consumption, making them suitable for industrial production.

[0067] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing high-purity rod-shaped hafnium boride powder, characterized in that, The method employing dual precursor-assisted mechanical synthesis includes the following steps: Step A: Under water bath conditions, add 15 mL of deionized water to a mixture of 3.81 g sodium tetraborate and 0.90 g sorbitol, and then stir until homogeneous to obtain mixture 1; perform solvothermal treatment of mixture 1 at 60-80 ℃ for 24-48 h to obtain a gel; dry and crush the gel to obtain boron-carbon precursor powder. Step B: Under water bath conditions, add 20 mL of ethanol to a mixture of 3.20 g hafnium chloride and 12 g acetylacetone, and then stir until homogeneous to obtain mixture 2; dry and crush mixture 2 to obtain hafnium precursor powder. Step C: Thoroughly mix the boron-carbon precursor powder and the hafnium precursor powder to obtain a mixed powder; place the mixed powder in a tube furnace and introduce protective gas into the tube furnace, and calcine at 1400-1700 ℃ for 60-180 min to obtain rod-shaped hafnium boride powder.

2. The method for preparing high-purity rod-shaped hafnium boride powder according to claim 1, characterized in that, In step A, the water bath temperature is 60-90 ℃; in step B, the water bath temperature is 60-75 ℃.

3. The method for preparing high-purity rod-shaped hafnium boride powder according to claim 1, characterized in that, In step A, the stirring speed for preparing mixture 1 is 100-600 rpm, and the stirring time is 20-120 min.

4. The method for preparing high-purity rod-shaped hafnium boride powder according to claim 1, characterized in that, In step B, the stirring speed for preparing mixture 2 is 200-450 rpm, and the stirring time is 120-300 min.

5. The method for preparing high-purity rod-shaped hafnium boride powder according to claim 1, characterized in that, The crushing method in steps A and B is ball milling, with a ball milling speed of 50-500 rpm and a ball milling time of 30-120 min.

6. The method for preparing high-purity rod-shaped hafnium boride powder according to claim 1, characterized in that, In step C, the gas flow rate of the protective gas is 0.005-50 L / min, the calcination temperature is 1500-1600 ℃, and the calcination time is 120-180 min.

7. The method for preparing high-purity rod-shaped hafnium boride powder according to claim 1 or 6, characterized in that, The protective gas mentioned in step C is one of argon, nitrogen, or helium.

8. A high-purity rod-shaped hafnium boride powder prepared by any one of claims 1-7.

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