HfC ceramic oxygen-free precursor, and preparation method and use thereof

Abstract

The application discloses a HfC ceramic precursor, a preparation method and application thereof. The chemical formula of the precursor is Hf(NR2) n (NX2) 4‑n , does not contain oxygen elements, and is converted into HfC ceramic by pyrolysis under an argon atmosphere at a temperature of 1300-2000 DEG C. The preparation method of the precursor is that amine exchange reaction is carried out between tetra-dimethylamino hafnium or tetra-diethylamino hafnium and an amine compound, and the HfC ceramic precursor is synthesized under mild conditions. The HfC ceramic precursor prepared by the application is suitable for being used as a matrix raw material of an ultra-high-temperature ceramic matrix composite.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ceramic precursor materials, and particularly relates to a HfC ceramic precursor, a preparation method and use thereof. BACKGROUND

[0002] HfC ceramic has excellent physical and chemical properties, such as super-high melting point, high hardness, wear resistance, good electrical and thermal conductivity, and chemical stability, and is an important super-high-temperature ceramic material, which can be applied to thermal protection components of high-speed aircrafts. Traditional synthesis methods of HfC ceramic include solid element combustion, oxide carbothermal reduction, chemical vapor deposition, etc., which generally require relatively harsh reaction conditions and have poor adaptability to forming processing requirements. Compared with traditional methods, ceramic precursor conversion method has the advantages of uniform and adjustable element composition, good precursor processing performance, and lower conversion temperature, which promotes the development of ceramic matrix composite and other fields, and ceramic precursor is an important raw material for the realization of this method.

[0003] Existing HfC ceramic precursors are mainly based on oxygen-containing systems, which rely on oxygen-containing ligands to stabilize the metal center. The main problem is that the pyrolysis product of the precursor has high residual oxygen content, and the high-temperature carbothermal reduction process is easy to damage the composite material fibers, which has an adverse effect on the performance of the final material. Therefore, the development of oxygen-free precursors has become the development direction of related material preparation and application. Limited by the high reactivity of the metal center and the types of ligands other than oxygen, there are few existing reports on oxygen-free HfC ceramic precursors, and the synthesis method is complex, and the product does not have a clear chemical structure, which is not conducive to the in-depth study and application of oxygen-free precursors. SUMMARY

[0004] The purpose of the present application is to provide a HfC ceramic precursor, a preparation method and use thereof.

[0005] The present application first provides a HfC ceramic precursor, which has a chemical formula of Hf(NR2) n (NX2) 4-n wherein NR2 is at least one of di-n-propylamino, di-isopropylamino, di-allylamino, di-n-butylamino, di-isobutylamino, di-n-pentylamino, tetrahydropyrrolyl, and hexahydropyridyl; NX2 is dimethylamino or diethylamino; and n is any integer or decimal number from 1 to 4, for example, 1, 2, 3, or 4.

[0006] In some embodiments, the HfC ceramic precursor has NR2 as di-n-propylamino, di-allylamino, or tetrahydropyrrolyl; and NX2 as dimethylamino or diethylamino.

[0007] As implementation, in the HfC ceramic precursor, when the NR2 is diallyl amino, the NX2 is diethyl amino; the n is 1, that is, the obtained HfC ceramic precursor is Hf(NR2)1(NX2)3;

[0008] Or, when the NR2 is di-n-propyl amino, the NX2 is diethyl amino; the n is 2, that is, the obtained HfC ceramic precursor is Hf(NR2)2(NX2)2;

[0009] Or, the NR2 is tetrahydropyrrole, and the n is 4, that is, the obtained HfC ceramic precursor is Hf(NR2)4.

[0010] The application further provides a preparation method of the HfC ceramic precursor, comprising: performing an amine exchange reaction on hafnium tetra-dimethylamide or hafnium tetra-diethylamide with an amine compound HNR2, and obtaining the HfC ceramic precursor through vacuum distillation.

[0011] According to an embodiment of the application, the amine exchange reaction is performed in an inert gas atmosphere, for example, in an argon atmosphere.

[0012] According to an embodiment of the application, in the above preparation method, the amine compound is at least one selected from di-n-propylamine, diisopropylamine, diallylamine, di-n-butylamine, diisobutylamine, di-n-pentylamine, tetrahydropyrrole and hexahydropyridine. The amine exchange reaction is performed on the amine compound HNR2 and the hafnium tetra-dimethylamide or hafnium tetra-diethylamide, and the by-product is dimethylamine or diethylamine with low boiling point. The HfC ceramic precursor is obtained after removing the low-boiling-point by-product through vacuum distillation. The HfC ceramic precursor has air sensitivity and should be stored in an inert gas environment.

[0013] According to an embodiment of the application, in the above preparation method, the molar ratio of the hafnium tetra-dimethylamide or hafnium tetra-diethylamide to the amine compound HNR2 is 1:1-1:4. The molar ratio of the raw materials determines the substitution ratio of the amine groups in the hafnium tetra-dimethylamide or hafnium tetra-diethylamide. If the amine compound is fed in too small amount (less than 1:1), the high-temperature residual weight of the product is low, and the product cannot be used as a ceramic precursor. If the upper limit (1:4) of the molar ratio of the amine compound is exceeded, all the original four dimethylamine groups or diethylamine groups are replaced.

[0014] In the above preparation method, the amine exchange reaction is performed at a temperature of 0-40℃, specifically 20-30℃.

[0015] In the above preparation method, the amine exchange reaction is performed for 4-24 hours, specifically 12-18 hours.

[0016] The application further provides a use of the HfC ceramic precursor as described above as an impregnation matrix to prepare a ceramic matrix composite material and a carbon / carbon composite material.

[0017] The application also provides a HfC ceramic, which is obtained by pyrolysis of the HfC ceramic precursor as described above.

[0018] According to an embodiment of the application, the pyrolysis method is pyrolysis of the HfC ceramic precursor at 1300-2000℃ for 1-12 hours, for example, at 1400-1600℃ for 1-5 hours, in an inert gas atmosphere, for example, in an argon atmosphere.

[0019] The application also provides a preparation method of the HfC ceramic as described above, which comprises: pyrolysis of the HfC ceramic precursor as described above.

[0020] According to an embodiment of the application, the pyrolysis reaction is pyrolysis of the HfC ceramic precursor at 1300-2000℃ for 1-12 hours, for example, at 1400-1600℃ for 1-5 hours, in an inert gas atmosphere, for example, in an argon atmosphere.

[0021] The application also provides use of the ceramic matrix composite and the carbon / carbon composite as described above in the field of aerospace, for example, use in preparation of a thermal protection component of a high-speed aircraft.

[0022] Compared with the prior art, the application has the following characteristics:

[0023] (1) The amino group is used as a ligand stabilizing the metal center, so that the prepared HfC ceramic precursor does not contain oxygen elements, which is conducive to reducing the residual oxygen content of the pyrolysis product, and the obtained HfC ceramic precursor is in a liquid state, which is suitable for various ceramic matrix composite processing technologies.

[0024] (2) The preparation method of the HfC ceramic precursor has mild conditions and good universality, which is conducive to large-scale preparation and meets different application requirements, and provides a key raw material for super-high-temperature ceramic matrix composite manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a nuclear magnetic hydrogen spectrum of the HfC ceramic precursor prepared in Example 1 of the application;

[0026] Figure 2 is an XRD graph of the pyrolysis product of the HfC ceramic precursor prepared in Example 1 of the application. DETAILED DESCRIPTION

[0027] The application will be further described below in combination with specific examples, but the application is not limited to the following examples. The methods are all conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified, and hafnium tetra-2-methylamino and hafnium tetra-2-ethylamino are prepared according to the method in the literature (J. Chem. Soc. (A) 1968, 1940).

[0028] Example 1

[0029] 100 mL three-necked flask was evacuated and filled with argon several times to replace the air, 4.35 g (9.3 mmol) of hafnium tetra-diethylamide was added, then 0.91 g (9.3 mmol) of diallylamine was added, the reaction was stirred at 20 °C for 18 hours, then the low boiling point substances were removed from the reaction by distillation under reduced pressure to obtain the liquid HfC ceramic precursor Hf(NR2)1(NX2)3, wherein NR2 is diallylamino and NX2 is diethylamino. Figure 1

[0030] The HfC ceramic precursor Hf(NR2)1(NX2)3 was pyrolyzed at 1500 °C for 2 hours in an argon atmosphere to obtain a black ceramic product, and the ceramic yield was 38.2%. XRD analysis showed that the product was HfC ceramic. Figure 2

[0031] Example 2

[0032] 100 mL three-necked flask was evacuated and filled with argon several times to replace the air, 6.44 g (13.8 mmol) of hafnium tetra-diethylamide was added, then 2.79 g (27.6 mmol) of di-n-propylamine was added, the reaction was stirred at 20 °C for 12 hours, then the low boiling point substances were removed from the reaction by distillation under reduced pressure to obtain the liquid HfC ceramic precursor Hf(NR2)2(NX2)2, wherein NR2 is di-n-propylamino and NX2 is diethylamino.

[0033] The HfC ceramic precursor Hf(NR2)2(NX2)2 was pyrolyzed at 1500 °C for 2 hours in an argon atmosphere to obtain a black ceramic product, and the ceramic yield was 26.6%. XRD analysis showed that the product was HfC ceramic.

[0034] Example 3

[0035] 100 mL three-necked flask was evacuated and filled with argon several times to replace the air, 3.44 g (9.7 mmol) of hafnium tetra-diethylamide was added, then 2.76 g (38.8 mmol) of tetrahydro-pyrrole was added, the reaction was stirred at 30 °C for 18 hours, then the low boiling point substances were removed from the reaction by distillation under reduced pressure to obtain the liquid HfC ceramic precursor Hf(NR2)4, wherein NR2 is tetrahydro-pyrrole group.

[0036] The HfC ceramic precursor Hf(NR2)4 was pyrolyzed at 1600 °C for 2 hours in an argon atmosphere to obtain a black ceramic product, and the ceramic yield was 47.8%. XRD analysis showed that the product was HfC ceramic.

[0037] ​​The above describes the embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, and the like made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. An HfC ceramic precursor, characterized in that, The chemical formula is Hf(NR2). n (NX2) 4-n , where NR2 is diallylamino; NX2 is dimethylamino or diethylamino; n is any integer or decimal from 1 to 4.

2. The HfC ceramic precursor according to claim 1, characterized in that, In the HfC ceramic precursor, when NR2 is diallylamino, NX2 is diethylamino; n is 1, that is, the resulting HfC ceramic precursor is Hf(NR2)1(NX2)3.

3. The method for preparing the HfC ceramic precursor according to claim 1 or 2, characterized in that, include: The HfC ceramic precursor is obtained by reacting tetramethylaminohafnium or tetramethylaminohafnium with an amine compound HNR2 via an amine exchange reaction and followed by vacuum distillation; wherein NR2 is diallylamino.

4. The preparation method according to claim 3, characterized in that, The amine exchange reaction is carried out in an inert gas atmosphere.

5. The preparation method according to claim 3, characterized in that, The molar ratio of tetradimethylaminohafnium or tetradiethylaminohafnium to the amine compound HNR2 is 1:1 to 1:4; NR2 is diallylamino.

6. The preparation method according to claim 3, characterized in that, The amine exchange reaction temperature is 0–40°C.

7. Use of the HfC ceramic precursor according to claim 1 or 2 as an impregnation matrix in the preparation of ceramic matrix composites and carbon / carbon composites.

8. An HfC ceramic, characterized in that, It is obtained by pyrolysis conversion of the HfC ceramic precursor described in claim 1 or 2.

9. The method for preparing the HfC ceramic according to claim 8, characterized in that, include: The HfC ceramic precursor described in claim 1 or 2 is subjected to a pyrolysis reaction.

10. The use of the ceramic matrix composite material and carbon / carbon composite material of claim 7 in the preparation of materials for the aerospace field.

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