Low-nitrogen low-oxygen hafnium tantalum carbon ceramic precursor and preparation method thereof

Abstract

The invention provides a low-nitrogen low-oxygen hafnium tantalum carbon ceramic precursor and a preparation method thereof, and belongs to the technical field of ceramic materials, the method comprises the following steps: preparing hafnium dichloride, a first hafnium intermediate and a second hafnium intermediate; mixing a first solvent, the first hafnium intermediate and the second hafnium intermediate, and reacting at 57-62 DEG C for 3.6-4.2 hours to obtain a hafnium carbide ceramic precursor; preparing tantalum trichloride, a first tantalum intermediate and a second tantalum intermediate; mixing a first solvent, the first tantalum intermediate and the second tantalum intermediate, and reacting at the temperature of 57-62 DEG C to obtain a tantalum carbide ceramic precursor; and mixing a third solvent, the nitrogen-containing weak ligand, the hafnium carbide ceramic precursor and the tantalum carbide ceramic precursor, and reacting at the temperature of 57-62 DEG C to obtain the low-nitrogen low-oxygen hafnium tantalum carbon ceramic precursor. The low-nitrogen low-oxygen hafnium-tantalum-carbon ceramic precursor disclosed by the invention has an important application prospect in high-temperature application in the fields of spaceflight, aviation and the like.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic materials, and in particular to a low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor and a preparation method thereof. Background Art

[0002] Hafnium-tantalum-carbon ceramic materials have broad application prospects in high-temperature applications such as aerospace and energy fields due to their excellent mechanical properties, heat resistance and chemical stability. At present, there are some methods for preparing precursors of hafnium-tantalum-carbon ceramic materials, including sol-gel method, deposition method and thermal decomposition method. However, these methods are affected by the nitrogen and oxygen content during the preparation process, resulting in uneven distribution of the components of the precursors of hafnium-tantalum-carbon ceramic materials, poor high-temperature stability, poor gas permeability, poor mechanical properties and heat resistance, and are not suitable for high-temperature applications in aerospace and aviation fields. Summary of the invention

[0003] In view of this, one of the purposes of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for preparing a low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor. The low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor prepared by this preparation method has low nitrogen and oxygen content, uniform distribution of components, high melting point, excellent oxidation resistance, poor high temperature stability, gas permeability, mechanical properties and heat resistance, and is suitable for high temperature applications in aerospace, aviation and other fields and has important application prospects.

[0004] A second object of the present invention is to provide a low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor.

[0005] In order to achieve one of the above purposes, the present invention adopts the following technical solution:

[0006] A method for preparing a low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor, the preparation method comprising the following steps:

[0007] Step S1, stirring a first solvent and hafnium tetrachloride into a first suspension, then slowly dropping a sodium cyclopentadienyl solution into the first suspension at a temperature of -10 to -5°C in an argon atmosphere, removing the residue, then heating to 90 to 100°C, recovering the first solvent, and finally purifying the first solvent and the second solvent by multiple times (2 to 4) through a gradient solvent to obtain hafnium dichloride;

[0008] Wherein, the mass ratio of the first solvent, hafnium tetrachloride and sodium cyclopentadienyl in the sodium cyclopentadienyl solution is 1:1 to 4:1;

[0009] Step S2, stirring and dispersing hafnium dichloride in a first solvent, then slowly adding a third solvent dropwise at a temperature of -10 to -5°C, and then heating to 0 to 50°C for reaction for 3.6 to 5.2 hours to obtain a first hafnium intermediate;

[0010] Wherein, the mass ratio of the hafnium dichloride, the first solvent and the third solvent is 1-6:1:1-4;

[0011] Step S3, stirring and dispersing hafnium dichloride in the first solvent, then adding a third solvent at a temperature of -25 to -20°C, introducing hydrogen, continuing stirring for 2 to 5 hours, then adding polyolefin, slowly raising the temperature to 78 to 82°C, reacting for 1.6 to 2.2 hours, to obtain a second hafnium intermediate;

[0012] Wherein, the mass ratio of the hafnium dichloride, the first solvent, the third solvent and the polyolefin is 1 to 3:1:1 to 2:1;

[0013] Step S4, mixing the first solvent, the first hafnium intermediate and the second hafnium intermediate in a mass ratio of 2 to 15:1 to 3:1, and reacting at a temperature of 57 to 62° C. for 3.6 to 4.2 hours to obtain a hafnium carbide ceramic precursor;

[0014] Step S5, stirring the first solvent and tantalum tetrachloride into a second suspension, then slowly dropping the sodium cyclopentadienyl solution into the second suspension in an argon atmosphere at a temperature of -10 to -5°C, removing the residue, then heating to 90 to 100°C, recovering the first solvent, and finally purifying multiple times through a gradient solvent of the first solvent and the second solvent to obtain tantalum trichloride;

[0015] Wherein, the mass ratio of the first solvent, tantalum tetrachloride and sodium cyclopentadienyl in the sodium cyclopentadienyl solution is 1:1 to 4:1;

[0016] Step S6, stirring and dispersing tantalum trichloride in the first solvent, then adding the third solvent at a temperature of -10 to -5°C, then heating to 0 to 50°C for reaction for 3.6 to 5.2 hours, and filtering to obtain a first tantalum intermediate;

[0017] Wherein, the mass ratio of the tantalum trichloride, the first solvent and the third solvent is 1-6:1:1-4;

[0018] Step S7, stirring and dispersing tantalum trichloride in the first solvent, then adding the third solvent at a temperature of -25 to -20°C, introducing hydrogen, continuing stirring to react for 2 to 5 hours, filtering, then adding polyolefin, slowly heating to 78 to 82°C and reacting for 1.6 to 2.2 hours to obtain a second tantalum intermediate;

[0019] Wherein, the mass ratio of tantalum trichloride, the first solvent, the third solvent and the polyolefin is 1 to 3:1:1 to 2:1;

[0020] Step S8, mixing the first solvent, the first tantalum intermediate and the second tantalum intermediate in a mass ratio of 2 to 15:1 to 3:1, and reacting at a temperature of 57 to 62° C. for 3.6 to 4.2 hours to obtain a tantalum carbide ceramic precursor;

[0021] Step S9, mixing the third solvent, the nitrogen-containing weak ligand, the hafnium carbide ceramic precursor and the tantalum carbide ceramic precursor in a mass ratio of 1-20:1-20:1-9:9-1, and reacting them at a temperature of 57-62° C. for 3.6-4.2 hours to obtain a low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor.

[0022] Furthermore, in step S1 and step S5, the gradient solvent is a mixed solvent of the first solvent and the second solvent in different mass ratios;

[0023] The mass ratio of the first solvent to the second solvent is two or more of 1:1, 2:1, 3:1 and 4:1.

[0024] Further, the first solvent is one or more of formic acid, tetrahydrofuran, acetone, chloroform, acetylacetone, cyclohexane, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, isopropanol, tert-butanol, and ethylenediamine;

[0025] The second solvent is one or more of methyl lithium, ethyl lithium, propyl lithium, butyl lithium, vinyl magnesium bromide, n-propenyl magnesium bromide, n-butenyl magnesium bromide, isobutenyl magnesium bromide, n-pentenyl magnesium bromide, and isopentenyl magnesium bromide.

[0026] Furthermore, in step S2 and step S6, the third solvent is one or more of benzene, toluene, dichloromethane, tetrahydrofuran, anhydrous ether, DMF, anhydrous methanol, anhydrous ethanol, and N-methylpyrrolidone.

[0027] Furthermore, in step S3 and step S7, the molecular weight of the polyolefin is 2,000 to 500,000.

[0028] Furthermore, in step S3 and step S7, the molecular weight of the polyolefin is 10,000 to 100,000.

[0029] Furthermore, the molecular weight of the polyolefin is 40,000-60,000.

[0030] Furthermore, the polyolefin is one or more of polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, poly-1-pentene, poly-1-hexene, and poly-1-octene.

[0031] Furthermore, in step S9, the nitrogen-containing weak ligand is one or more of pyridine, quinoline, imine and aziridine.

[0032] In order to achieve the second objective above, the present invention adopts the following technical solution:

[0033] A low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor is prepared by the above-mentioned preparation method.

[0034] The beneficial effects of the present invention are:

[0035] The invention discloses a hafnium carbide ceramic precursor and a tantalum carbide ceramic precursor prepared by using hafnium dichloride and tantalum trichloride. In the synthesis process, oxygen and nitrogen elements are strictly controlled not to be introduced, thereby reducing the oxygen and nitrogen content of the low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor, improving the ceramic yield, and ensuring the high-temperature stability and gas permeability of the hafnium tantalum carbon ceramic material. The hafnium tantalum carbon ceramic material has excellent mechanical properties, heat resistance and ablation resistance, and can be used to prepare high-temperature resistant coatings, fiber reinforcements and ceramic-based composite matrixes, meeting the requirements of high-temperature applications in the fields of aerospace and aviation. The invention has the advantages of simple preparation process, low cost and high yield. points; the components of the low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor of the present invention are evenly distributed, which is helpful to obtain a uniform ceramic material microstructure; the oxygen content of the low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor of the present invention is 1.90-2.00%, the nitrogen content is 0.10-0.15%, the 1400°C ceramic yield is 47.14-47.62%, the 1600°C ceramic yield is 39.34-39.65%, the line ablation rate is 0.0028-0.036mm / s, and the prepared hafnium tantalum composite material has a 900°C bending strength of 500-550MPa, and a 1600°C bending strength of 605-638MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a scanning electron microscope image of a ceramic product of a low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor at 1400°C in Example 1;

[0037] Figure 2 This is a TGA curve diagram of the low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor in Example 1;

[0038] Figure 3 This is the DSC curve of the low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor in Example 1. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0040] Embodiment 1:

[0041] (1) Preparation of Hafnium Carbide Ceramic Precursor

[0042] Add 2g of acetone and 4g of hafnium tetrachloride to the reaction container and stir to form a suspension. In an argon atmosphere, at a temperature of -10°C, slowly drop 2g of sodium cyclopentadienyl in the sodium cyclopentadienyl solution to remove the residue, heat to 90°C to recover acetone and obtain a solid. Purify the solid three times with a gradient solvent of acetone and ethyl lithium to obtain dichlorodiphenylamine. Among them, the mass ratio of acetone to ethyl lithium during the three purifications is 1:1, 2:1 and 3:1.

[0043] Under argon protection, in a reaction container, 4 g of hafnium dichloride was stirred and dispersed in 2 g of acetone, 3 g of dichloromethane was slowly added dropwise at -10°C, the temperature was raised to 0°C after the addition was complete, and the reaction was carried out for 3.6 hours, and the first hafnium intermediate solution was obtained by suction filtration.

[0044] Under argon protection, 4g of dichlorodiphenylmethane was stirred and dispersed in 2g of acetone in a reaction container, and 3g of dichloromethane was slowly added dropwise at a temperature of -22°C. After the addition was complete, hydrogen was introduced and the stirring was continued until the reaction lasted for 4h. The solid was removed by suction filtration, and 2g of polypropylene with a molecular weight of 10,000 was added to the obtained reaction solution. After slowly heating to 80°C for reaction for 2 hours, the temperature was continued to be raised to recover acetone and dichloromethane, and the degree of polymerization was adjusted to obtain the second hafnium intermediate.

[0045] In an anhydrous and oxygen-free atmosphere, acetone, the first hafnium intermediate and the second hafnium intermediate are added to a reaction container, reacted at 60° C. for 4 hours, and the acetone is recovered to obtain a hafnium carbide ceramic precursor, wherein the mass ratio of acetone, the first hafnium intermediate and the second hafnium intermediate is 10:2:1.

[0046] (2) Preparation of Tantalum Carbide Ceramic Precursor

[0047] Add 2g of acetone and 4g of tantalum tetrachloride to the reaction container and stir to form a suspension. In an argon atmosphere, at a temperature of -7°C, slowly drop 2g of sodium cyclopentadienyl solution to remove the residue, heat to 95°C to recover acetone, and obtain a solid. The solid is purified three times by a gradient solvent of acetone and ethyl lithium to obtain tantalum trichloride. Among them, the mass ratio of acetone to ethyl lithium during the three purifications is 1:1, 2:1 and 3:1.

[0048] Under argon protection, in a reaction container, 4 g of tantalum trichloride was stirred and dispersed in 2 g of acetone, 3 g of dichloromethane was slowly added dropwise at a temperature of -10°C, and after the addition was complete, the temperature was raised to 0°C and the reaction was carried out for 3.6 hours, and the first tantalum intermediate solution was obtained by suction filtration.

[0049] Under argon protection, 4g of tantalum trichloride was stirred and dispersed in 2g of acetone in a reaction container, and 3g of dichloromethane was slowly added at a temperature of -22°C. After the addition was complete, hydrogen was introduced and the stirring was continued until the reaction lasted for 4h. The solid was removed by suction filtration, and 2g of polypropylene with a molecular weight of 10,000 was added to the obtained reaction solution. After slowly heating to 80°C for reaction for 2 hours, the temperature was continued to be raised to recover acetone and dichloromethane, and the degree of polymerization was adjusted to obtain the second tantalum intermediate.

[0050] In an anhydrous and oxygen-free atmosphere, acetone, a first tantalum intermediate and a second tantalum intermediate are added to a reaction container, reacted at 60° C. for 4 hours, and acetone is recovered to obtain a tantalum carbide ceramic precursor. The mass ratio of acetone, the first tantalum intermediate and the second tantalum intermediate is 10:2:1.

[0051] (3) Preparation of low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor

[0052] In an anhydrous and oxygen-free atmosphere, 2 g of dichloromethane, 2 g of pyridine, 1 g of hafnium carbide ceramic precursor and 9 g of tantalum carbide ceramic precursor were added into a reaction container and stirred, reacted at 60° C. for 4 hours, and filtered to obtain 5 g of low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor.

[0053] The mass percentages of C, O, N, hafnium (Hf) and tantalum (Ta) in the low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor of this embodiment are 27.45%, 1.98%, 0.15%, 31.63% and 38.79% respectively.

[0054] In an argon atmosphere, the obtained low-nitrogen and low-oxygen hafnium tantalum carbon precursor was solidified and then subjected to cracking tests at 1400°C and 1600°C, respectively. The ceramic yield under these conditions was calculated and shown in Table 1.

[0055] The hafnium tantalum carbon ceramic matrix composite material of this embodiment was subjected to ablation resistance test using a supersonic flame, and ablated for 20 seconds at a high temperature of 3000K. Its linear ablation rate is shown in Table 1. The mechanical properties (flexural strength MPa) of the composite materials prepared with different precursors are compared in Table 2. The scanning electron microscope image, TGA curve graph and DSC curve graph of the 1400°C ceramic product of the low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor are shown in Table 2. Figure 1 , Figure 2 and 3 shown.

[0056] Embodiment 2:

[0057] (1) Preparation of Hafnium Carbide Ceramic Precursor

[0058] Add 2g of cyclohexane and 6g of hafnium tetrachloride to the reaction vessel and stir to form a suspension. In an argon atmosphere, at a temperature of -7°C, slowly drop 2g of sodium cyclopentadienyl in the sodium cyclopentadienyl solution to remove the residue, heat to 95°C to recover cyclohexane, and obtain a solid. Purify the solid twice by a gradient solvent of cyclohexane and butyl lithium to obtain dichlorodiphenylamine. Among them, the mass ratio of cyclohexane to butyl lithium during the two purifications is 2:1 and 3:1.

[0059] Under argon protection, in a reaction container, 2 g of hafnium dichloride was stirred and dispersed in 2 g of cyclohexane, and 2 g of dichloromethane was slowly added dropwise at -7°C. After the addition was complete, the temperature was raised to 20°C and the reaction was carried out for 4 hours. The first hafnium intermediate solution was obtained by suction filtration.

[0060] Under argon protection, 2g of dichlorodiphenylmethane was stirred and dispersed in 2g of cyclohexane in a reaction container, and 2g of dichloromethane was slowly added dropwise at a temperature of -25°C. After the addition was complete, hydrogen was introduced and the stirring was continued until the reaction lasted for 2h. The solid was removed by suction filtration, and 2g of polyethylene with a molecular weight of 5000 was added to the obtained reaction solution. After slowly heating to 78°C and reacting for 1.6 hours, the temperature of cyclohexane and dichloromethane was continued to be raised to adjust the degree of polymerization to obtain the second hafnium intermediate.

[0061] In an anhydrous and oxygen-free atmosphere, cyclohexane, the first hafnium intermediate and the second hafnium intermediate are added to a reaction container, reacted at 57° C. for 3.6 hours, and the cyclohexane is recovered to obtain a hafnium carbide ceramic precursor, wherein the mass ratio of cyclohexane, the first hafnium intermediate and the second hafnium intermediate is 2:1:1.

[0062] (2) Preparation of Tantalum Carbide Ceramic Precursor

[0063] Add 2g of cyclohexane and 6g of tantalum tetrachloride to the reaction vessel and stir to form a suspension. In an argon atmosphere, at a temperature of -10°C, slowly drop 2g of sodium cyclopentadienyl in the sodium cyclopentadienyl solution to remove the residue, heat and recover the cyclohexane to obtain a solid. The solid is purified twice by a gradient solvent of cyclohexane and butyl lithium to obtain tantalum trichloride. Among them, the mass ratio of cyclohexane to butyl lithium during the two purifications is 2:1 and 3:1.

[0064] Under argon protection, in a reaction container, 2 g of tantalum trichloride was dispersed in 2 g of cyclohexane with stirring, and 2 g of dichloromethane was slowly added dropwise at -7°C. After the addition was complete, the temperature was raised to 20°C and the reaction was carried out for 4 hours. The first tantalum intermediate solution was obtained by suction filtration.

[0065] Under the protection of argon, 2g of tantalum trichloride was stirred and dispersed in 2g of cyclohexane in a reaction container, and 2g of dichloromethane was slowly added at a temperature of -25°C. After the addition was complete, hydrogen was introduced and the stirring was continued until the reaction lasted for 2h. The solid was removed by suction filtration, and 2g of polyethylene with a molecular weight of 5000 was added to the obtained reaction solution. After slowly heating to 78°C for reaction for 1.6 hours, the temperature was continued to be raised to recover cyclohexane and dichloromethane, and the degree of polymerization was adjusted to obtain the second tantalum intermediate.

[0066] In an anhydrous and oxygen-free atmosphere, cyclohexane, a first tantalum intermediate and a second tantalum intermediate are added to a reaction container, reacted at 57° C. for 3.6 hours, and the cyclohexane is recovered to obtain a tantalum carbide ceramic precursor. The mass ratio of cyclohexane, the first tantalum intermediate and the second tantalum intermediate is 2:1:1.

[0067] (3) Preparation of low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor

[0068] In an anhydrous and oxygen-free atmosphere, 2 g of dichloromethane, 2 g of pyridine, 2 g of hafnium carbide ceramic precursor and 2 g of tantalum carbide ceramic precursor were added into a reaction container and stirred, reacted at 57° C. for 3.6 hours, and filtered to obtain a low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor.

[0069] The mass percentages of C, O, N, hafnium (Hf) and tantalum (Ta) in the low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor of this embodiment are 26.45%, 2.00%, 0.13%, 32.15% and 39.47% respectively.

[0070] In an argon atmosphere, the obtained low-nitrogen and low-oxygen hafnium tantalum carbon precursor was solidified and then subjected to cracking tests at 1400°C and 1600°C, respectively. The ceramic yield under these conditions was calculated and shown in Table 1.

[0071] The hafnium-tantalum-carbon ceramic-based composite material of this embodiment was subjected to an ablation resistance test using a supersonic flame. The ablation was performed at a high temperature of 3000K for 20 seconds. The linear ablation rate is shown in Table 1.

[0072] Embodiment 3:

[0073] (1) Preparation of Hafnium Carbide Ceramic Precursor

[0074] Add 2g of formic acid and 8g of hafnium tetrachloride to the reaction vessel and stir to form a suspension. In an argon atmosphere, at a temperature of -5°C, slowly drop 2g of sodium cyclopentadienyl in the sodium cyclopentadienyl solution to remove the residue, heat to 100°C, recover the formic acid, and obtain a solid. Purify the solid four times with a gradient solvent of formic acid and propyl lithium to obtain dichlorodiphenylamine. Among them, the mass ratio of formic acid to propyl lithium during the four purifications is 1:1, 2:1, 3:1 and 4:1.

[0075] Under argon protection, in a reaction container, 12 g of hafnium dichloride was stirred and dispersed in 2 g of formic acid, 8 g of toluene was slowly added dropwise at -5°C, and after the addition was complete, the temperature was raised to 50°C and reacted for 5.2 hours, and the first hafnium intermediate solution was obtained by suction filtration.

[0076] Under argon protection, 6 g of hafnium dichloride was stirred and dispersed in 2 g of formic acid in a reaction container, and 4 g of toluene was slowly added dropwise at a temperature of -20°C. After the addition was complete, hydrogen was introduced and the stirring was continued until the reaction lasted for 5 hours. The solid was removed by suction filtration, and 2 g of poly-1-pentene with a molecular weight of 500,000 was added to the obtained reaction solution. After slowly heating to 82°C for reaction for 2.2 hours, the temperature was continued to be raised to recover formic acid and toluene, and the degree of polymerization was adjusted to obtain the second hafnium intermediate.

[0077] In an anhydrous and oxygen-free atmosphere, formic acid, the first hafnium intermediate and the second hafnium intermediate are added to a reaction container, reacted at 62° C. for 4.2 hours, and the formic acid is recovered to obtain a hafnium carbide ceramic precursor, wherein the mass ratio of formic acid, the first hafnium intermediate and the second hafnium intermediate is 15:3:1.

[0078] (2) Preparation of Tantalum Carbide Ceramic Precursor

[0079] Add 2g of formic acid and 8g of tantalum tetrachloride to the reaction vessel and stir to form a suspension. In an argon atmosphere, at a temperature of -5°C, slowly drop 2g of sodium cyclopentadienyl in the sodium cyclopentadienyl solution to remove the residue, heat to 100°C to recover formic acid, and obtain a solid. The solid is purified four times by a gradient solvent of formic acid and propyl lithium to obtain tantalum trichloride. Among them, the mass ratio of formic acid to propyl lithium during the four purifications is 1:1, 2:1, 3:1 and 4:1.

[0080] Under argon protection, in a reaction container, 12 g of tantalum trichloride was dispersed in 2 g of formic acid with stirring, and 8 g of toluene was slowly added dropwise at -5°C. After the addition was complete, the temperature was raised to 50°C and the reaction was carried out for 5.2 hours. The first tantalum intermediate solution was obtained by suction filtration.

[0081] Under argon protection, 6g of tantalum trichloride was stirred and dispersed in 2g of formic acid in a reaction container, and 4g of toluene was slowly added dropwise at a temperature of -20°C. After the addition was complete, hydrogen was introduced and the stirring was continued until the reaction lasted for 5h. The solid was removed by suction filtration, and 2g of poly-1-pentene at 500000 was added to the obtained reaction solution. After slowly heating to 82°C for reaction for 2.2 hours, the temperature was continued to be raised to recover formic acid and toluene, and the degree of polymerization was adjusted to obtain the second tantalum intermediate.

[0082] In an anhydrous and oxygen-free atmosphere, formic acid, a first tantalum intermediate and a second tantalum intermediate are added to a reaction container, reacted at 62° C. for 4.2 hours, and the dissolved formic acid is recovered to obtain a tantalum carbide ceramic precursor. The mass ratio of formic acid, the first tantalum intermediate and the second tantalum intermediate is 15:3:1.

[0083] (3) Preparation of low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor

[0084] In an anhydrous and oxygen-free atmosphere, 20 g of toluene, 20 g of aziridine, 9 g of hafnium carbide ceramic precursor and 1 g of tantalum carbide ceramic precursor were added into a reaction container and stirred, reacted at 62° C. for 4.2 hours, and filtered to obtain a low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor.

[0085] The mass percentages of C, O, N, hafnium (Hf) and tantalum (Ta) in the low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor of this embodiment are 27.45%, 1.95%, 0.13%, 31.65% and 38.82% respectively.

[0086] In an argon atmosphere, the obtained low-nitrogen and low-oxygen hafnium tantalum carbon precursor was solidified and then subjected to cracking tests at 1400°C and 1600°C, respectively. The ceramic yield under these conditions was calculated and shown in Table 1.

[0087] The hafnium-tantalum-carbon ceramic-based composite material of this embodiment was subjected to an ablation resistance test using a supersonic flame. The ablation was performed at a high temperature of 3000K for 20 seconds. The linear ablation rate is shown in Table 1.

[0088] The mechanical properties of the hafnium tantalum carbon ceramic composite materials prepared using the low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursors of Examples 1 to 3 are shown in Table 2.

[0089] Table 1 Performance indicators of the low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursors of Examples 1 to 3.

[0090]

[0091] Table 2 Mechanical properties of composite materials prepared in Examples 1 to 3

[0092] Composite materials prepared in the examples 900℃ flexural strength (MPa) 1600℃ flexural strength (MPa) Example 1 Preparation of composite materials 550 638 Example 2 Preparation of composite materials 512 610 Example 3 Preparation of composite materials 535 614

[0093] The above examples are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the best embodiment, a person skilled in the art should understand that the technical solution of the present invention can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor, characterized in that: The preparation method comprises the following steps: Step S1, stirring a first solvent and hafnium tetrachloride into a first suspension, then slowly dropping a sodium cyclopentadienyl solution into the first suspension at a temperature of -10 to -5°C in an argon atmosphere, removing the residue, then heating to 90 to 100°C, recovering the first solvent, and finally purifying the first solvent and the second solvent by gradient solvent for multiple times to obtain hafnium dichloride; Wherein, the mass ratio of the first solvent, hafnium tetrachloride and sodium cyclopentadienyl in the sodium cyclopentadienyl solution is 1:1 to 4:1; Step S2, stirring and dispersing hafnium dichloride in a first solvent, then slowly adding a third solvent dropwise at a temperature of -10 to -5°C, and then heating to 0 to 50°C for reaction for 3.6 to 5.2 hours to obtain a first hafnium intermediate; Wherein, the mass ratio of the hafnium dichloride, the first solvent and the third solvent is 1-6:1:1-4; Step S3, stirring and dispersing hafnium dichloride in the first solvent, then adding a third solvent at a temperature of -25 to -20°C, introducing hydrogen, continuing stirring for 2 to 5 hours, then adding polyolefin, slowly raising the temperature to 78 to 82°C, reacting for 1.6 to 2.2 hours, to obtain a second hafnium intermediate; Wherein, the mass ratio of the hafnium dichloride, the first solvent, the third solvent and the polyolefin is 1 to 3:1:1 to 2:1; Step S4, mixing the first solvent, the first hafnium intermediate and the second hafnium intermediate in a mass ratio of 2 to 15:1 to 3:1, and reacting at a temperature of 57 to 62° C. for 3.6 to 4.2 hours to obtain a hafnium carbide ceramic precursor; Step S5, stirring the first solvent and tantalum tetrachloride into a second suspension, then slowly dropping the sodium cyclopentadienyl solution into the second suspension in an argon atmosphere at a temperature of -10 to -5°C, removing the residue, then heating to 90 to 100°C, recovering the first solvent, and finally purifying multiple times through a gradient solvent of the first solvent and the second solvent to obtain tantalum trichloride; Wherein, the mass ratio of the first solvent, tantalum tetrachloride and sodium cyclopentadienyl in the sodium cyclopentadienyl solution is 1:1 to 4:1; Step S6, stirring and dispersing tantalum trichloride in the first solvent, then adding the third solvent at a temperature of -10 to -5°C, then heating to 0 to 50°C for reaction for 3.6 to 5.2 hours, and filtering to obtain a first tantalum intermediate; Wherein, the mass ratio of the tantalum trichloride, the first solvent and the third solvent is 1-6:1:1-4; Step S7, stirring and dispersing tantalum trichloride in the first solvent, then adding the third solvent at a temperature of -25 to -20°C, introducing hydrogen, continuing stirring to react for 2 to 5 hours, filtering, then adding polyolefin, slowly heating to 78 to 82°C and reacting for 1.6 to 2.2 hours to obtain a second tantalum intermediate; Wherein, the mass ratio of tantalum trichloride, the first solvent, the third solvent and the polyolefin is 1 to 3:1:1 to 2:1; Step S8, mixing the first solvent, the first tantalum intermediate and the second tantalum intermediate in a mass ratio of 2 to 15:1 to 3:1, and reacting at a temperature of 57 to 62° C. for 3.6 to 4.2 hours to obtain a tantalum carbide ceramic precursor; Step S9, mixing the third solvent, the nitrogen-containing weak ligand, the hafnium carbide ceramic precursor and the tantalum carbide ceramic precursor in a mass ratio of 1-20:1-20:1-9:9-1, and reacting them at a temperature of 57-62° C. for 3.6-4.2 hours to obtain a low-nitrogen and low-oxygen hafnium tantalum carbon ceramic precursor.

2. The preparation method according to claim 1, characterized in that: In step S1 and step S5, the gradient solvent is a mixed solvent of a first solvent and a second solvent in different mass ratios; The mass ratio of the first solvent to the second solvent is two or more of 1:1, 2:1, 3:1 and 4:

1.

3. The preparation method according to claim 2, characterized in that: The first solvent is one or more of formic acid, tetrahydrofuran, acetone, chloroform, acetylacetone, cyclohexane, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, isopropanol, tert-butanol, and ethylenediamine; The second solvent is one or more of methyl lithium, ethyl lithium, propyl lithium, butyl lithium, vinyl magnesium bromide, n-propenyl magnesium bromide, n-butenyl magnesium bromide, isobutenyl magnesium bromide, n-pentenyl magnesium bromide, and isopentenyl magnesium bromide.

4. The preparation method according to any one of claims 1 to 3, characterized in that: In step S2 and step S6, the third solvent is one or more of benzene, toluene, dichloromethane, tetrahydrofuran, anhydrous ether, DMF, anhydrous methanol, anhydrous ethanol, and N-methylpyrrolidone.

5. The preparation method according to claim 4, characterized in that: In the step S3 and the step S7, the molecular weight of the polyolefin is 2000-500000.

6. The preparation method according to claim 5, characterized in that: In the step S3 and the step S7, the molecular weight of the polyolefin is 10,000 to 100,000.

7. The preparation method according to claim 6, characterized in that: The molecular weight of the polyolefin is 40,000-60,000.

8. The preparation method according to claim 7, characterized in that: The polyolefin is one or more of polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, poly-1-pentene, poly-1-hexene, and poly-1-octene.

9. The preparation method according to claim 8, characterized in that: In the step S9, the nitrogen-containing weak ligand is one or more of pyridine, quinoline, imine and aziridine.

10. A low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor, characterized in that: The low-nitrogen and low-oxygen hafnium-tantalum-carbon ceramic precursor is prepared by the preparation method described in any one of claims 1 to 9.

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