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

Abstract

The invention relates to HfC-coated SiC-coated C core-shell nanopowder and a preparation method thereof, belongs to the technical field of surface modification of ultrahigh-temperature ceramic powder, and solves the technical problems of long process period, high cost and difficulty in ensuring coating uniformity of a process for coating carbon on the surfaces of ultrahigh-temperature modified silicon carbide ceramic particles. Preparing a modified HfC coupling solution; adding resorcinol into the modified HfC coupling solution, and stirring to obtain an intermediate solution; sequentially adding formaldehyde and ammonia water, and stirring until phenolic aldehyde is formed to obtain a cross-linked mixed solution; the cross-linked mixed solution is centrifugally dried, centrifugally dried powder is placed into ethyl alcohol and deionized water to be cleaned, the cleaned powder is dried and cured, and HfC-coated RF powder is obtained; and cracking the HfC-coated RF powder to obtain the HfC-coated SiC-coated C core-shell type nano powder. The preparation method is used for preparing the core-shell type nano powder.

Description

Technical Field

[0001] The invention belongs to the technical field of surface modification of ultra-high temperature ceramic powders, and specifically relates to a HfC@SiC@C core-shell nano powder and a preparation method thereof. Background Art

[0002] Continuous carbon fiber reinforced ultra-high temperature modified silicon carbide ceramic matrix composites (abbreviated as: C f / SiC-UHTCs) overcome the low damage tolerance of ceramics, and have both the extremely high melting point of ultra-high temperature ceramics and the good oxidation resistance of SiC ceramics. They are widely used in the hoods, leading edges of wings, control rudders, etc. of advanced aircraft. f A lot of process research has been carried out at home and abroad on SiC-UHTCs composite materials, such as SI / RMI, CVI / RMI, Sol-gel / RMI, CVI / SI / RMI, CVI / PIP / RMI, etc. Usually, after impregnating UHTCs particles, CVI-C or PIP-C is used to achieve carbon coating on the surface of UHTCs particles. Combined with the RMI process, many advantages of composite materials such as high density, low cost, and low residual porosity can be achieved. However, the above two carbon coating process methods have long cycles, high costs, and it is difficult to ensure coating uniformity. Summary of the invention

[0003] In order to overcome the shortcomings of long process cycle, high cost and difficult to ensure coating uniformity in the surface coating of ultra-high temperature modified silicon carbide ceramic particles, the present invention proposes a HfC@SiC@C core-shell nanopowder and a preparation method thereof.

[0004] The technical solution adopted by the present invention to solve the technical problem is:

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

[0006] Step S1, HfC modification

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

[0008] Step S2, preparing modified HfC coupling solution

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

[0010] Step S3, adding resorcinol

[0011] Resorcinol was added to the modified HfC coupling solution and stirred until uniform to obtain an intermediate solution.

[0012] Step S4, cross-linking

[0013] Formaldehyde and ammonia water are added to the intermediate solution in sequence, and the mixture is stirred until the hydroquinone-formaldehyde condenses to form phenolic formaldehyde, thereby obtaining a cross-linked mixed solution.

[0014] Step S5, centrifugal drying and curing

[0015] Using a centrifuge, centrifugally drying the cross-linked mixed solution to obtain a centrifugally dried powder;

[0016] Place the centrifugally dried powder in ethanol and deionized water and wash 1 to 3 times;

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

[0018] Step S6, lysis

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

[0020] In the above preparation method, in step S1, during HfC modification, the temperature of mixing the tetramethylammonium hydroxide aqueous solution and the HfC powder is 30°C to 100°C, and the stirring time is 30min to 120min; the drying temperature T2 is 150 to 200°C.

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

[0022] In the above preparation method, in step S3, resorcinol is added in an amount of 1 g to 20 g, the stirring temperature is 20° C. to 30° C., and the stirring time is 30 min to 60 min.

[0023] In the above preparation method, in step S4, during the cross-linking, the weight of formaldehyde is 1 g to 20 g, the weight of ammonia water is 1 g to 20 g, the stirring temperature is 20° C. to 30° C., and the stirring time is 12 h to 24 h.

[0024] In the above-mentioned preparation method, in step S5, during the centrifugal drying and curing, the curing temperature is 150° C. to 200° C., and the curing time is 1 h to 2 h.

[0025] In the above preparation method, in step S6, during the pyrolysis, the pyrolysis temperature is 800°C to 1000°C, the pyrolysis time is 10 min to 120 min, and the cooling rate from the tube furnace temperature to room temperature is less than 5°C / 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 to obtain the corresponding UHTCs particle surface carbon-coated core-shell nanopowder.

[0027] A HfC@SiC@C core-shell nano powder is prepared by the above-mentioned preparation method.

[0028] The beneficial effects of the present invention are:

[0029] A method for preparing HfC@SiC@C core-shell nanopowders is disclosed. The HfC@SiC@C core-shell nanopowders are prepared by a bulk polycondensation reaction of resorcinol-formaldehyde, and a uniformly coated carbon layer is obtained on the surface of ultra-high temperature ceramic particles. By regulating the concentration of resorcinol-formaldehyde, the coated carbon layer of different thicknesses is achieved, the wetting behavior of the particle surface is improved, the wetting dynamics are increased, and the UHTCs particles are dispersed in the mass.

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

[0031] A method for preparing HfC@SiC@C core-shell nanopowder realizes controllable thickness of carbon layer in HfC@SiC@C powder by increasing the number of polycondensation reactions of resorcinol-formaldehyde.

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

[0033] A method for preparing HfC@SiC@C core-shell nanopowder. The prepared HfC@SiC@C powder has a core-shell structure, can inhibit the growth of UHTC grains at high temperature, and prevent the mechanical properties of UHTCs from decreasing with the growth of grains; 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of the preparation method of an embodiment of the present invention;

[0035] Figure 2 This is a macroscopic picture of the HfC@SiC@C core-shell nanopowder after drying according to an embodiment of the present invention;

[0036] Figure 3 This is a macroscopic image of the HfC@SiC@C core-shell nanopowder after solidification according to an embodiment of the present invention;

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

[0038] Figure 5 Transmission electron microscope (TEM) morphology of HfC@SiC@C core-shell nanopowder prepared in the embodiment of the present invention;

[0039] Figure 6 Transmission electron microscope (TEM) morphology of HfC@SiC@C core-shell nanopowder prepared in the embodiment of the present invention;

[0040] Figure 7 Element distribution (Mapping) of HfC@SiC@C core-shell nanopowder prepared in an embodiment of the present invention. DETAILED DESCRIPTION

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

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

[0043] S1. A tetramethylammonium hydroxide (TMAH) aqueous solution (modification solution) is mixed with HfC particles, and then heated and stirred in a water bath for a certain period of time, and then centrifuged and washed until neutral and then 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°C, the time t1 is 30-120min, and the drying temperature T2 is 150-200°C.

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

[0045] S3, in step S2, 1-20 g of resorcinol is added in sequence and stirred thoroughly. The stirring temperature T4 is 20-30° C., and the time t3 is 30-60 min.

[0046] S4: In step S3, 1-20 g of formaldehyde and 1-20 g of ammonia water are added in sequence and stirred at room temperature to carry out polycondensation reaction. The cross-linking temperature T5 is 20-30° C. and the time t4 is 12-24 h.

[0047] S5, the obtained mixed solution is centrifugally dried to obtain dark red powder, which is then washed with ethanol and deionized water for 1 to 3 times, and placed in an oven for curing to obtain HfC@RF. The curing temperature T6 is 150 to 200°C, and the time t5 is 1 to 2 hours.

[0048] S6. In step S5, the HfC@RF powder is placed in a high-purity N2 atmosphere tube furnace for pyrolysis, and then cooled to room temperature at a cooling 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 10-120min.

[0049] Embodiment 1, 2, 3

[0050] A method for preparing HfC@SiC@C core-shell nanopowder, the parameters in the implementation steps 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: The following steps are involved: Step S1, HfC modification: The tetramethylammonium hydroxide aqueous solution and the HfC powder are mixed and stirred, heated in a water bath, centrifuged and washed until neutral, and dried to obtain a modified HfC powder; Step S2, preparing a modified HfC coupling solution: Adding modified HfC powder and KH-560 silane coupling agent to a mixed solution of deionized water and ethanol, stirring until uniform, to obtain a modified HfC coupling solution; Step S3, adding resorcinol: Add resorcinol to the modified HfC coupling solution and stir until uniform to obtain an intermediate solution; Step S4, cross-linking: In the intermediate solution, formaldehyde and ammonia water are added in sequence, and stirred until the hydroquinone-formaldehyde condenses to form phenolic formaldehyde, thereby obtaining a cross-linked mixed solution; Step S5, centrifugal drying and solidification: Using a centrifuge, centrifugally drying the cross-linked mixed solution to obtain a centrifugally dried powder; Place the centrifugally dried powder in ethanol and deionized water and wash 1 to 3 times; The cleaned powder is dried and solidified in an oven to obtain HfC@RF powder; Step S6, lysis: The HfC@RF powder was placed in a high-purity N2 atmosphere tube furnace for cracking. After the cracking was completed, the temperature of the tube furnace dropped to room temperature to obtain HfC@SiC@C core-shell nanopowder.

2. The preparation method according to claim 1, characterized in that: In the step S1, during the HfC modification, the temperature of the tetramethylammonium hydroxide aqueous solution and the HfC powder being mixed and stirred is 30°C to 100°C, and the stirring time is 30min to 120min; and the drying temperature is 150°C to 200°C.

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

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

5. The preparation method according to claim 4, characterized in that: In the step S4, during the cross-linking, the weight of formaldehyde is 1 g to 20 g, and the weight of ammonia water is 1 g to 20 g; the stirring temperature is 20° C. to 30° C., and the stirring time is 12 h to 24 h.

6. The preparation method according to claim 5, characterized in that: In the step S5, during centrifugal drying and curing, the curing temperature is 150° C. to 200° C. and the curing time is 1 hour to 2 hours.

7. The preparation method according to claim 6, characterized in that: In the step S6, during the cracking, the cracking temperature is 800° C. to 1000° C., the cracking time is 10 min to 120 min; and the cooling rate from the tubular furnace temperature to room temperature is less than 5° C. / min.

8. The preparation method according to claim 1, characterized in that: In the 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; and the corresponding UHTCs particle surface carbon-coated core-shell nanopowder can be obtained.

9. A HfC@SiC@C core-shell nanopowder, characterized in that: Prepared by any preparation method according to claims 1 to 8.

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