HfC@SiC@C core-shell type nanopowder and a preparation method thereof

Abstract

The application relates to an HfC@SiC@C core-shell type nanopowder and a preparation method thereof, and belongs to the technical field of surface modification of ultrahigh-temperature ceramic powder. The technical problems of long process period, high cost and difficult uniformity guarantee of the surface coating carbon process of the ultrahigh-temperature modified silicon carbide ceramic particles are solved. The preparation method comprises the following steps: HfC modification; preparation of a modified HfC coupling solution; addition of resorcinol into the modified HfC coupling solution and stirring to obtain an intermediate solution; addition of formaldehyde and ammonia water in sequence and stirring until phenolic aldehyde is formed to obtain a crosslinking mixed solution; centrifugal drying of the crosslinking mixed solution; cleaning of the centrifugal dried powder in ethanol and deionized water; and drying and solidification of the cleaned powder to obtain HfC@RF powder; and pyrolysis of the HfC@RF powder to obtain the HfC@SiC@C core-shell type nanopowder. The preparation method is used for the preparation of the core-shell type nanopowder.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high temperature ceramic powder surface modification technology, specifically relating to an HfC@SiC@C core-shell nanopowder and its preparation method. Background Technology

[0002] Continuous carbon fiber reinforced ultra-high temperature modified silicon carbide ceramic matrix composite (abbreviated as: C f / SiC-UHTCs) overcome the low damage tolerance of ceramics while possessing the extremely high melting point of ultra-high temperature ceramics and the good oxidation resistance of SiC ceramics, and are widely used in advanced aircraft such as nose cones, wing leading edges, and control surfaces. Currently, the preparation of C using combined processes is being studied. f Extensive research has been conducted both domestically and internationally on the processing of SiC-UHTCs composites, including methods such as SI / RMI, CVI / RMI, Sol-gel / RMI, CVI / SI / RMI, and CVI / PIP / RMI. Typically, after impregnating UHTCs particles, CVI-C or PIP-C is used to achieve carbon coating on the particle surface. Combining this with RMI technology can achieve numerous advantages in composite materials, including high density, low cost, and low residual porosity. However, the aforementioned two carbon coating processes are time-consuming, costly, and difficult to guarantee uniform coating. Summary of the Invention

[0003] To overcome the shortcomings of the ultra-high temperature modified silicon carbide ceramic particle surface carbon coating process, such as long cycle, high cost, and difficulty in ensuring coating uniformity, this invention proposes a HfC@SiC@C core-shell nanopowder and its preparation method.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] A method for preparing HfC@SiC@C core-shell nanopowder includes the following steps:

[0006] Step S1, HfC modification

[0007] The tetramethylammonium hydroxide aqueous solution was mixed and stirred with HfC powder, heated in a water bath, centrifuged and washed until neutral, and dried to obtain modified HfC powder.

[0008] Step S2, prepare the modified HfC coupling solution

[0009] Modified HfC powder and KH-560 silane coupling agent were added to a mixed solution of deionized water and ethanol and stirred until homogeneous to obtain a modified HfC coupling solution.

[0010] Step S3, add resorcinol

[0011] Add resorcinol to the modified HfC coupling solution and stir until homogeneous to obtain an intermediate solution.

[0012] Step S4, crosslinking

[0013] In the intermediate solution, formaldehyde and ammonia are added sequentially and stirred until the hydroquinone-formaldehyde condensation reaction forms phenolic resin, thus obtaining a cross-linked mixed solution.

[0014] Step S5, centrifugal drying and curing

[0015] The cross-linked mixture solution was dried by centrifugation to obtain a centrifuged and dried powder.

[0016] Place the centrifuged dried powder into ethanol and deionized water and wash it 1 to 3 times.

[0017] The cleaned powder was dried and cured in an oven to obtain HfC@RF powder.

[0018] Step S6, pyrolysis

[0019] HfC@RF powder was placed in a tube furnace under a high-purity N2 atmosphere for pyrolysis. After pyrolysis was completed, the temperature of the tube furnace was reduced to room temperature to obtain HfC@SiC@C core-shell nanopowder.

[0020] In the above preparation method, in step S1, the temperature for mixing and stirring the tetramethylammonium hydroxide aqueous solution with HfC powder is 30℃~100℃, and the stirring time is 30min~120min; the drying temperature T2 is 150~200℃.

[0021] In the above preparation method, step S2, in preparing the modified HfC coupling solution, the weight of the modified HfC powder is 5g-20g, and the weight of the KH-560 silane coupling agent is 0.1g-0.3g. In the mixed solution of deionized water and ethanol, the amount of deionized water is 300mL-400mL, and the amount of ethanol is 100mL-200mL. The stirring temperature is 20℃-30℃, and the stirring time is 10min-60min.

[0022] In the above preparation method, step S3 involves adding resorcinol, where the weight of resorcinol is 1g to 20g. The stirring temperature is 20℃ to 30℃, and the stirring time is 30min to 60min.

[0023] In the above preparation method, in step S4, during crosslinking, the weight of formaldehyde is 1g to 20g and the weight of ammonia is 1g to 20g. The stirring temperature is 20℃ to 30℃, and the stirring time is 12h to 24h.

[0024] In the above preparation method, in step S5, during centrifugal drying and curing, the curing temperature is 150℃~200℃ and the curing time is 1h~2h.

[0025] In the above preparation method, in step S6, during pyrolysis, the pyrolysis temperature is 800℃~1000℃, and the pyrolysis time is 10min~120min. The cooling rate of the tube furnace to room temperature is less than 5℃ / min.

[0026] In the above preparation method, in step S1, HfC modification, HfC powder can be replaced by HfB2, or HfC powder can be replaced by ZrC, or HfC powder can be replaced by ZrB2, or HfC powder can be replaced by TaC. This yields core-shell nanoparticles with carbon coating on the surface of the corresponding UHTCs particles.

[0027] A core-shell type HfC@SiC@C nanopowder was prepared using the method described above.

[0028] The beneficial effects of this invention are:

[0029] A method for preparing HfC@SiC@C core-shell nanoparticles is disclosed. The method involves the bulk polycondensation reaction of resorcinol and formaldehyde to obtain a uniformly thick carbon coating layer on the surface of ultra-high temperature ceramic particles. By controlling the concentration of resorcinol and formaldehyde, different thicknesses of the carbon coating layer are achieved, improving the wetting behavior and wetting dynamics of the particle surface, thus enabling the UHTCs particles to be dispersed throughout the aggregate.

[0030] A method for preparing HfC@SiC@C core-shell nanopowder is disclosed, which controls the content of phenolic resin formed by the polycondensation reaction of resorcinol-formaldehyde by adjusting the mass ratio of HfC powder and resorcinol, thereby achieving controllable carbon layer thickness in HfC@SiC@C powder.

[0031] A method for preparing HfC@SiC@C core-shell nanopowder, which achieves controllable carbon layer thickness in HfC@SiC@C powder by controlling the number of resorcinol-formaldehyde condensation reactions.

[0032] A method for preparing HfC@SiC@C core-shell nanopowder is characterized by simple operation, high repeatability, short preparation cycle, and suitability for industrial production.

[0033] A method for preparing HfC@SiC@C core-shell nanopowder is disclosed. The prepared HfC@SiC@C powder has a core-shell structure, which can inhibit the growth of UHTC grains at high temperatures and prevent the mechanical properties of UHTCs from decreasing with grain growth. The outer carbon phase can improve the fracture toughness and thermal conductivity of the material matrix. The outer carbon phase in the prepared HfC@SiC@C powder can effectively reduce the elastic modulus of HfC particles and reduce the generation of matrix cracks. Attached Figure Description

[0034] Figure 1 This is a flowchart of the preparation method according to an embodiment of the present invention;

[0035] Figure 2 This is a macroscopic image of the HfC@SiC@C core-shell nanopowder after drying, as described in an embodiment of the present invention.

[0036] Figure 3 This is a macroscopic image of the HfC@SiC@C core-shell nanopowder after curing, as described in an embodiment of the present invention.

[0037] Figure 4 This is a macroscopic image of the HfC@SiC@C core-shell nanopowder after pyrolysis in an embodiment of the present invention;

[0038] Figure 5 The transmission electron microscopy (TEM) morphology of HfC@SiC@C core-shell nanopowder prepared in the embodiments of the present invention;

[0039] Figure 6 The transmission electron microscopy (TEM) morphology of HfC@SiC@C core-shell nanopowder prepared in the embodiments of the present invention;

[0040] Figure 7 Elemental distribution (mapping) of HfC@SiC@C core-shell nanopowder prepared for embodiments of the present invention. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0042] A method for preparing HfC@SiC@C core-shell nanopowder, which utilizes the bulk polycondensation reaction of resorcinol-formaldehyde to achieve carbon coating on the surface of HfC ultra-high temperature ceramic powder, includes the following steps:

[0043] S1. HfC particles are mixed with a tetramethylammonium hydroxide (TMAH) aqueous solution (modifying solution), then heated and stirred in a water bath for a certain time. After centrifugation and washing until neutral, the mixture is dried to obtain modified HfC powder. The powder includes, but is not limited to, HfB2, ZrC, ZrB2, TaC, etc. The heating temperature T1 is 30–100℃, the time t1 is 30–120 min, and the drying temperature T2 is 150–200℃.

[0044] S2. Add 5-20g of modified HfC powder and 0.1-0.3g of KH-560 silane coupling agent to 300-400mL of deionized water and 100-200mL of ethanol, and mix and stir for a certain period of time. The mixed solution is a coupling solution, the stirring temperature T3 is 20-30℃, and the stirring time t2 is 10-60min.

[0045] In steps S3 and S2, 1-20g of resorcinol are added sequentially and stirred thoroughly. The stirring temperature T4 is 20-30℃, and the stirring time t3 is 30-60min.

[0046] In steps S4 and S3, 1-20g of formaldehyde and 1-20g of ammonia are added sequentially and stirred at room temperature to carry out the polycondensation reaction. The crosslinking temperature T5 is 20-30℃, and the time t4 is 12-24h.

[0047] S5. The resulting mixed solution is centrifuged and dried to obtain a dark red powder, which is then washed 1-3 times with ethanol and deionized water, and cured in an oven to obtain HfC@RF. The curing temperature T6 is 150-200℃, and the time t5 is 1-2h.

[0048] In steps S6 and S5, the HfC@RF powder is placed in a tube furnace under a high-purity N2 atmosphere for pyrolysis, and then cooled to room temperature at a rate of less than 5°C / min to obtain black HfC@SiC@C powder. The pyrolysis temperature T7 is 800–1000°C, and the time t6 is 10–120 min.

[0049] Examples 1, 2, and 3

[0050] A method for preparing HfC@SiC@C core-shell nanopowder, the parameters of which are shown in Table 1.

[0051] Table 1

[0052]

[0053]

Claims

1. A method for preparing HfC@SiC@C core-shell nanopowder, characterized in that, Includes the following steps: Step S1, HfC modification: The tetramethylammonium hydroxide aqueous solution was mixed and stirred with HfC powder, heated in a water bath, centrifuged and washed until neutral, and dried to obtain modified HfC powder. Step S2, prepare the modified HfC coupling solution: Modified HfC powder and KH-560 silane coupling agent were added to a mixed solution of deionized water and ethanol and stirred until homogeneous to obtain a modified HfC coupling solution. Step S3, add resorcinol: Add resorcinol to the modified HfC coupling solution and stir until homogeneous to obtain an intermediate solution; Step S4, crosslinking: In the intermediate solution, formaldehyde and ammonia are added sequentially and stirred until the hydroquinone-formaldehyde condensation reaction forms phenolic resin, thus obtaining a cross-linked mixed solution; Step S5, centrifugal drying and curing: The cross-linked mixture solution was dried by centrifugation to obtain a centrifuged and dried powder. Place the centrifuged dried powder into ethanol and deionized water and wash it 1-3 times. The cleaned powder was dried and cured in an oven to obtain HfC@RF powder; Step S6, pyrolysis: HfC@RF powder was placed in a tube furnace under a high-purity N2 atmosphere for pyrolysis. After pyrolysis was completed, the temperature of the tube furnace was reduced to room temperature to obtain HfC@SiC@C core-shell nanopowder.

2. The preparation method according to claim 1, characterized in that, In step S1, during HfC modification, the temperature for mixing and stirring the tetramethylammonium hydroxide aqueous solution with HfC powder is 30℃~100℃, and the stirring time is 30min~120min; the drying temperature is 150℃~200℃.

3. The preparation method according to claim 2, characterized in that, In step S2, the modified HfC coupling solution is prepared by using 5g~20g of modified HfC powder and 0.1g~0.3g of KH-560 silane coupling agent. The mixed solution of deionized water and ethanol is prepared by using 300mL~400mL of deionized water and 100mL~200mL of ethanol. The stirring temperature is 20℃~30℃ and the stirring time is 10min~60min.

4. The preparation method according to claim 3, characterized in that, In step S3, resorcinol is added, with a weight of 1g to 20g; the stirring temperature is 20℃ to 30℃, and the stirring time is 30min to 60min.

5. The preparation method according to claim 4, characterized in that, In step S4, during crosslinking, the weight of formaldehyde is 1g~20g and the weight of ammonia is 1g~20g; the stirring temperature is 20℃~30℃ and the stirring time is 12h~24h.

6. The preparation method according to claim 5, characterized in that, In step S5, during centrifugal drying and curing, the curing temperature is 150℃~200℃ and the curing time is 1h~2h.

7. The preparation method according to claim 6, characterized in that, In step S6, during pyrolysis, the pyrolysis temperature is 800℃~1000℃, and the pyrolysis time is 10min~120min; the cooling rate of the tube furnace to room temperature is less than 5℃ / min.

8. A core-shell type HfC@SiC@C nanopowder, characterized in that, Prepared using any one of the preparation methods according to claims 1 to 7.

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