A nano-Hf6Ta2O 17 Coated Graphite Particle Composite Powder, Preparation Method and Application

Abstract

This invention relates to a nano-Hf6Ta2O 17 Coated flake graphite particle composite powder, its preparation method and application, and a nano-Hf6Ta2O are disclosed. 17 The preparation method of the composite powder coated with flake graphite particles is as follows: Pretreated flake graphite particles are dispersed in anhydrous ethanol and ultrasonically vibrated. Hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) are then added to form a homogeneous solution. Finally, a certain amount of concentrated nitric acid, polyethylene glycol (PEG), and water are added, and the mixture is heated and stirred at 50–70°C to form a sol. The sol is then thoroughly dried in an 80°C forced-air drying oven and heat-treated at 600–1200°C for 2–3 hours to obtain Hf6Ta2O. 17 Coated flake graphite particle composite powder. The prepared coated composite powder effectively slows down the oxidation rate of flake graphite particles in a high-temperature aerobic environment, improving their oxidation sensitivity when used in the aerospace field.

Description

Technical Field

[0001] This invention belongs to the field of oxidation protection technology and relates to a nano-Hf6Ta2O 17 Composite powders coated with flake graphite particles, their preparation methods, and applications. Background Technology

[0002] Carbon / graphite materials possess a range of excellent properties, such as low density, high specific strength, and good thermal shock resistance, making them widely used in hot-end components in the aerospace field, such as electric furnace heating elements, engine throat liners, and nozzles. However, carbon / graphite materials exhibit extremely high oxidation sensitivity, beginning to oxidize in oxygen-rich environments above 370°C, accompanied by a rapid decline in mechanical properties, thus severely limiting their application in these fields. Ultra-high temperature ceramics, with their high melting point, excellent chemical stability, and low oxygen diffusion coefficient, are the preferred materials for protecting carbon / graphite materials from oxidation and ablation.

[0003] Document 1 "Li H, Yu Y, Wang S, et al. Low thermal conductivity Hf6Ta2O 17 "Ceramics fabricated by solvothermal and pressure-less sintering, Ceramics International, 2021, 47(12): 17711-17718." This report describes the preparation of Hf6Ta2O using a hydrothermal method combined with pressureless sintering. 17 The ceramic was found to have a thermal conductivity of approximately 1.62 W / (m·K) at 1500℃.

[0004] Reference 2, "McCormack S, Tseng K, Weber R, et al. In situ determination of the HfO2-Ta2O5-temperature phase diagram up to 3000℃, Journal of the American Ceramic Society, 2018, 8: 4848-4861," plotted the HfO2-Ta2O5 binary phase diagram and found Hf6Ta2O 17 Its melting point is approximately 2450℃.

[0005] Reference 3, "Wang Y, Xiong X, Li G, et al. Preparation and ablation properties of Hf(Ta)C co-deposition coating for carbon / carbon composites[J]. Corrosion Science, 2013, 66: 177-182," reports on Hf(Ta)C coatings prepared by chemical vapor deposition, and finds that Hf6Ta2O forms in the oxide layer. 17 Solid solutions exhibit a low oxygen diffusion coefficient, resulting in coatings exhibiting good ablation performance.

[0006] However, there is currently a lack of simple, low-cost, and short-cycle methods for preparing carbon / graphite composite powders coated with ultra-high temperature ceramic oxide solid solutions. To address the aforementioned application needs and research status, this paper proposes a simple, low-cost, and short-cycle method for preparing carbon / graphite composite powders coated with ultra-high temperature ceramic oxide solid solutions. This method will effectively improve the oxidation sensitivity of carbon / graphite materials and expand their application range in high-temperature aerobic environments. Summary of the Invention

[0007] Technical problems to be solved

[0008] To avoid the shortcomings of existing technologies, this invention proposes a nano-Hf6Ta2O 17 The present invention relates to a composite powder coated with flake graphite particles, its preparation method, and its application. Compared with the prior art, the composite powder proposed in this invention can effectively alleviate the oxidation sensitivity of carbon / graphite materials and improve their application potential in high-temperature oxygen-containing environments.

[0009] Technical solution

[0010] A nano-Hf6Ta2O 17 A composite powder coated with flake-like graphite particles, characterized by comprising a surface layer and an inner layer coated within the surface layer; the surface layer is nano-Hf6Ta2O. 17 The inner layer consists of flake-shaped graphite particles.

[0011] The composite powder contains 10 wt% to 30 wt% flake graphite particles.

[0012] A nano-Hf6Ta2O 17 A method for preparing composite powder coated with flake-shaped graphite particles, characterized by the following steps:

[0013] Step 1: Under an Ar atmosphere, the initial flake graphite particles were treated in concentrated nitric acid and then washed until neutral.

[0014] Step 2: Disperse the pretreated flake graphite particles in anhydrous ethanol and sonicate for 30-60 min. Then, weigh hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) at a hafnium to tantalum molar ratio of 3:2, dissolve them in anhydrous ethanol, and stir thoroughly to obtain a homogeneous solution. The total content of hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) in the solution is 10 wt% to 30 wt%.

[0015] Step 3: Place the above solution on a magnetic stirrer and heat and stir, then slowly add concentrated nitric acid, polyethylene glycol (PEG), and water in sequence, stirring continuously until a sol is formed. Then place it in a forced-air drying oven to dry thoroughly.

[0016] The concentrated nitric acid comprises 10wt% to 25wt%, polyethylene glycol (PEG) comprises 1wt% to 3wt%, and water comprises 1wt% to 2wt%.

[0017] Step 4: The dried powder is placed in a corundum boat and heat-treated in a muffle furnace at 600–1200℃ for 2–3 hours. Then it is cooled to room temperature and thoroughly ground to obtain nano-Hf6Ta2O with a coated structure. 17 Composite powder with coated flake graphite particles.

[0018] Before the concentrated nitric acid treatment in step 1, the sample is heat-treated at 300-500°C for 3-5 hours, then soaked in concentrated nitric acid for 0.5-1 hour, and finally washed with distilled water until neutral.

[0019] The concentration of the concentrated nitric acid is 65% to 68%.

[0020] The polyethylene glycol (PEG) has a relative molecular weight of 180–220.

[0021] The temperature of the heating stirrer in step 3 is 50-70°C, and the temperature of the forced-air drying oven is 80°C.

[0022] The heating rate during the heat treatment in step 4 is 4℃ / min to 10℃ / min.

[0023] A nano-Hf6Ta2O 17 The application of composite powder coated with flake graphite particles is characterized by its use in the manufacture of hot-end components in the aerospace field, including but not limited to electric furnace heating elements, engine throat liners, or nozzles.

[0024] Beneficial effects

[0025] This invention proposes a nano-Hf6Ta2O 17 Coated flake graphite particle composite powder, its preparation method and application, and a nano-Hf6Ta2O are disclosed. 17The preparation method of the composite powder coated with flake graphite particles is as follows: Pretreated flake graphite particles are dispersed in anhydrous ethanol and ultrasonically vibrated. Hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) are then added to form a homogeneous solution. Finally, a certain amount of concentrated nitric acid, polyethylene glycol (PEG), and water are added, and the mixture is heated and stirred at 50–70°C to form a sol. The sol is then thoroughly dried in an 80°C forced-air drying oven and heat-treated at 600–1200°C for 2–3 hours to obtain Hf6Ta2O. 17 Coated flake graphite particle composite powder. The prepared coated composite powder effectively slows down the oxidation rate of flake graphite particles in a high-temperature aerobic environment, improving their oxidation sensitivity when used in the aerospace field.

[0026] Compared with the prior art, the beneficial effects of the method of the present invention are as follows:

[0027] 1. Using hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) as precursors, anhydrous ethanol as solvent, and a small amount of additives, Hf6Ta2O was rapidly obtained by low-temperature heat treatment in an Ar atmosphere. 17 The preparation method for coating flake graphite particles into composite powder is characterized by simple operation, simple equipment, high efficiency and low cost.

[0028] 2. Surface Hf6Ta2O 17 It is a nano-sized powder with good dispersibility, high crystallinity and purity;

[0029] 3. Compared with uncoated flake graphite particles, the oxidation rate of composite powder is significantly reduced, which will improve its current situation of exhibiting extremely strong oxidation sensitivity when used in high-temperature and oxygen-containing environments.

[0030] Figure 1 SEM images of pure flake graphite particles and the prepared composite powder, from... Figure 1 It can be seen that the composite powder prepared by the present invention has a layer of nanoparticles coated on the graphite sheet particles; Figure 2 To prepare the XRD pattern of the composite powder, from Figure 2 It can be seen that the composite powder obtained by this invention forms a single-phase Hf6Ta2O with high purity and crystallinity in the graphite flake particles. 17 . Figure 3 TGA test results for pure graphite flakes and the preparation of composite powders, from Figure 3 It can be seen that by coating the surface of flake graphite particles with nano-Hf6Ta2O... 17 This significantly reduces its oxidation rate. Attached Figure Description

[0031] Figure 1 SEM images of pure flake graphite particles and the prepared composite powder.

[0032] Figure 2 XRD patterns of composite powders

[0033] Figure 3 TGA test results for pure flake graphite particles and the preparation of composite powders Detailed Implementation

[0034] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0035] Example 1:

[0036] Step 1: The initial flake graphite particles were heat-treated at 400℃ for 4 hours under Ar atmosphere, then soaked in concentrated nitric acid for 0.5 hours, and finally washed with distilled water until neutral.

[0037] Step 2: Disperse the pretreated flake graphite particles in anhydrous ethanol and sonicate for 30 min. Then, weigh a certain amount of hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) precursors according to a hafnium to tantalum molar ratio of 3:2 and dissolve them in anhydrous ethanol (20 wt% of the precursors). Stir thoroughly to obtain a homogeneous solution.

[0038] Step 3: Place the above solution on a magnetic stirrer and heat and stir, then slowly add 20wt% concentrated nitric acid, 2wt% polyethylene glycol (PEG) and 2wt% water in sequence. Continue stirring at 70°C until a sol is formed, then place it in an 80°C forced-air drying oven to dry thoroughly.

[0039] Step 4: The dried powder was placed in a corundum boat and heat-treated in a tube furnace at 1000℃ for 2 hours at a heating rate of 5℃ / min. It was then cooled to room temperature and thoroughly ground to obtain single-phase Hf6Ta2O. 17 Composite powders coated with flake-shaped graphite particles.

[0040] Example 2:

[0041] Step 1: The initial flake graphite particles were heat-treated at 400℃ for 4 hours under Ar atmosphere, then soaked in concentrated nitric acid for 0.5 hours, and finally washed with distilled water until neutral.

[0042] Step 2: Disperse the pretreated flake graphite particles in anhydrous ethanol and sonicate for 30 min. Then, weigh a certain amount of hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) precursors according to a hafnium to tantalum molar ratio of 3:1 and dissolve them in anhydrous ethanol (20 wt% of the precursors). Stir thoroughly to obtain a homogeneous solution.

[0043] Step 3: Place the above solution on a magnetic stirrer and heat and stir, then slowly add 20wt% concentrated nitric acid, 2wt% polyethylene glycol (PEG) and 2wt% water in sequence. Continue stirring at 70°C until a sol is formed, then place it in an 80°C forced-air drying oven to dry thoroughly.

[0044] Step 4: The dried powder is placed in a corundum boat and heat-treated in a tube furnace at 1000℃ for 2 hours at a heating rate of 5℃ / min. Then it is cooled to room temperature and thoroughly ground to obtain a composite powder of HfO2 and TaC coated flake graphite particles.

[0045] Example 3:

[0046] Step 1: The initial flake graphite particles were heat-treated at 400℃ for 4 hours under Ar atmosphere, then soaked in concentrated nitric acid for 0.5 hours, and finally washed with distilled water until neutral.

[0047] Step 2: Disperse the pretreated flake graphite particles in anhydrous ethanol and sonicate for 30 min. Then, weigh a certain amount of hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) precursors according to a hafnium to tantalum molar ratio of 3:2 and dissolve them in anhydrous ethanol (20 wt% of the precursors). Stir thoroughly to obtain a homogeneous solution.

[0048] Step 3: Place the above solution on a magnetic stirrer and heat and stir, then slowly add 20wt% concentrated nitric acid, 2wt% polyethylene glycol (PEG) and 2wt% water in sequence. Continue stirring at 70°C until a sol is formed, then place it in an 80°C forced-air drying oven to dry thoroughly.

[0049] Step 4: The dried powder was placed in a corundum boat and heat-treated in a tube furnace at 1000℃ for 2 hours at a heating rate of 5℃ / min. It was then cooled to room temperature and thoroughly ground to obtain Hf6Ta2O. 17 Composite powder of Ta2O5-coated flake graphite particles.

[0050] The above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any simple modifications or improvements to the process that are not substantially different from the concept of the present invention without departing from the core of the present invention are within the scope of protection of the present invention.

Claims

1. A nano-Hf6Ta2O 17 The composite powder coated with flake graphite particles is characterized by... It includes a surface layer and an inner layer encapsulated within the surface layer; the surface layer is nano-Hf6Ta2O. 17 The inner layer consists of flake-shaped graphite particles; The nano-Hf6Ta2O 17 The composite powder coated with flake graphite particles is prepared according to the following steps: Step 1: Heat-treat the initial flake graphite particles at 300~500℃ for 3~5h, then soak them in concentrated nitric acid under Ar atmosphere for 0.5~1h, and finally wash them with distilled water until neutral. Step 2: Disperse the pretreated flake graphite particles in anhydrous ethanol and sonicate for 30-60 min. Then, weigh hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) at a hafnium to tantalum molar ratio of 3:2, dissolve them in anhydrous ethanol, and stir thoroughly to obtain a homogeneous solution. The total content of hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) in the solution is 10 wt% to 30 wt%. Step 3: Place the above solution on a magnetic stirrer and heat and stir, then slowly add concentrated nitric acid, polyethylene glycol (PEG), and water in sequence, stirring continuously until a sol is formed. Then place it in a forced-air drying oven to dry thoroughly. The concentrated nitric acid comprises 10wt%~25wt%, polyethylene glycol (PEG) comprises 1wt%~3wt%, and water comprises 1wt%~2wt%. Step 4: The dried powder is placed in a corundum boat and heat-treated in a muffle furnace at 600~1200℃ for 2~3 hours. Then it is cooled to room temperature and thoroughly ground to obtain nano-Hf6Ta2O with a coating structure. 17 Composite powder with coated flake graphite particles.

2. The nano-Hf6Ta2O according to claim 1 17 The composite powder coated with flake-shaped graphite particles is characterized by: The composite powder contains 10wt% to 30wt% flake graphite particles.

3. A nano-Hf6Ta2O as described in claim 1 or 2 17 The method for preparing composite powder coated with flake graphite particles is characterized by: The steps are as follows: Step 1: Heat-treat the initial flake graphite particles at 300~500℃ for 3~5h, then soak them in concentrated nitric acid under Ar atmosphere for 0.5~1h, and finally wash them with distilled water until neutral. Step 2: Disperse the pretreated flake graphite particles in anhydrous ethanol and sonicate for 30-60 min. Then, weigh hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) at a hafnium to tantalum molar ratio of 3:2, dissolve them in anhydrous ethanol, and stir thoroughly to obtain a homogeneous solution. The total content of hafnium tetrachloride (HfCl4) and tantalum pentachloride (TaCl5) in the solution is 10 wt% to 30 wt%. Step 3: Place the above solution on a magnetic stirrer and heat and stir, then slowly add concentrated nitric acid, polyethylene glycol (PEG), and water in sequence, stirring continuously until a sol is formed. Then place it in a forced-air drying oven to dry thoroughly. The concentrated nitric acid comprises 10wt%~25wt%, polyethylene glycol (PEG) comprises 1wt%~3wt%, and water comprises 1wt%~2wt%. Step 4: The dried powder is placed in a corundum boat and heat-treated in a muffle furnace at 600~1200℃ for 2~3 hours. Then it is cooled to room temperature and thoroughly ground to obtain nano-Hf6Ta2O with a coating structure. 17 Composite powder with coated flake graphite particles.

4. The method according to claim 3, characterized in that: The concentration of the concentrated nitric acid is 65%~68%.

5. The method according to claim 3, characterized in that: The polyethylene glycol (PEG) has a relative molecular weight of 180-220.

6. The method according to claim 3, characterized in that: The temperature of the heating stirrer in step 3 is 50-70°C, and the temperature of the forced-air drying oven is 80°C.

7. The method according to claim 3, characterized in that: The heating rate during the heat treatment in step 4 is 4℃ / min to 10℃ / min.

8. A nano-Hf6Ta2O as described in claim 1 or 2 17 The application of composite powders coated with flake graphite particles is characterized by: Manufacturing of hot-end components used in the aerospace field, including electric furnace heating elements, engine throat liners, or nozzles.

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