SiC@C-Si composite powder with core-shell structure for thermal spraying and preparation method thereof

Abstract

The application discloses a SiC@C-Si composite powder with a core-shell structure for thermal spraying and a preparation method thereof, and comprises the following steps: 1) performing heat treatment on polydopamine-coated SiC particles to obtain SiC@C powder; 2) mixing the SiC@C powder obtained in the step 1) with Si to obtain mixed powder, and then mixing the mixed powder with a polyvinyl alcohol solution, deionized water and anhydrous ethanol, and performing ball milling to obtain a slurry suspension; and 3) performing spray granulation on the slurry suspension obtained in the step 2) to obtain the SiC@C-Si composite powder with the core-shell structure for thermal spraying. The composite powder prepared by the method can be directly used for thermal spraying, and can form a SiC thermal spraying coating which is well matched with the thermal expansion of a C / C composite material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of surface coating and relates to SiC@C-Si composite powder with core-shell structure for thermal spraying and a preparation method thereof. BACKGROUND

[0002] C / C composite material is a key strategic material for high-speed aircraft super-high-temperature hot end parts, but it is highly sensitive to oxidation, and long-life stable service in a high-temperature oxygen-containing environment needs to consider thermal protection strategies. SiC has high physical and chemical compatibility with C / C and high thermal stability, and can generate a continuous, uniform and dense SiO2 glass protective film after high-temperature oxidation, and is considered to be an ideal thermal protection coating material for C / C composite material. Thermal spraying represented by plasma spraying and flame spraying has high coating deposition efficiency, great thermal influence on the substrate, and no limitation on the size of spraying, and is a commonly used method for preparing thermal protection coatings on the surface of C / C composite material. However, SiC particles do not have a liquid phase and are easy to decompose at high temperature of plasma jet, and SiC particles inevitably oxidize during atmospheric thermal spraying, causing serious thermal loss of SiC powder, which cannot be directly used for plasma spraying.

[0003] In order to solve the problem that SiC cannot be directly used for thermal spraying, carbides (such as ZrC and TaC), borides (ZrB2 and Yb2O3) and rare earth compounds (LaB6 and La2O3) are usually added as the second phase to modify SiC, and a SiC-rich coating on the surface of C / C composite material is obtained by means of thermal stable deposition of the second phase in plasma spraying. However, the modified SiC coating of carbides, borides and rare earth compounds has the problem of mismatching with the thermal expansion coefficient of C / C composite material, which easily causes cracking and failure. SUMMARY

[0004] The application aims to overcome the shortcomings of the prior art and provides SiC@C-Si composite powder with core-shell structure for thermal spraying and a preparation method thereof. The composite powder prepared by the method can be directly used for thermal spraying and can form a SiC thermal spraying coating with good thermal expansion matching with C / C composite material.

[0005] To achieve the above-mentioned purpose, the application discloses a preparation method of SiC@C-Si composite powder with core-shell structure for thermal spraying, which comprises the following steps:

[0006] 1) heat treating polydopamine-coated SiC particles to obtain SiC@C powder;

[0007] 2) mixing the SiC@C powder obtained in step 1) with Si to obtain mixed powder, and mixing the mixed powder with polyvinyl alcohol solution, deionized water and anhydrous ethanol and then ball milling to obtain a slurry suspension;

[0008] 3) spray granulation of the slurry suspension obtained in step 2) to obtain SiC@C-Si composite powder with core-shell structure for thermal spraying.

[0009] The process of step 3) is as follows:

[0010] The slurry suspension obtained in step 2) is pumped into a spray granulation device by a peristaltic pump, the slurry suspension is atomized into droplets by centrifugal force generated by a rotating nozzle, and heat convection occurs with high-temperature dry air, so that the water in the droplets evaporates and coagulates to form SiC@C-Si composite powder with core-shell structure for thermal spraying.

[0011] Before step 1), it further includes:

[0012] 11) Dissolve tris(hydroxymethyl)aminomethane and SiC in deionized water, stir uniformly, and adjust the pH value to obtain a SiC uniformly dispersed solution;

[0013] 12) Add dopamine hydrochloride to the SiC uniformly dispersed solution obtained in step 1), stir, separate by suction filtration, and dry the obtained product to obtain polydopamine-coated SiC particles.

[0014] In step 11), the mass ratio of tris(hydroxymethyl)aminomethane to SiC is (2-3):96.

[0015] In step 11), the pH value is adjusted to 9.5 by hydrochloric acid.

[0016] In step 12), the mass ratio of dopamine hydrochloride to SiC in the SiC uniformly dispersed solution is (5-6):96.

[0017] The operation process of step 1) is as follows:

[0018] The polydopamine-coated SiC particles obtained in step 2) are heat treated at 800-1000℃ under an argon atmosphere.

[0019] In step 2), the mass ratio of the mixed powder, PVA solution, deionized water and anhydrous ethanol is (1-5):(1-5):1:1.

[0020] In the spray granulation process of step 3), the inlet temperature is 300-350℃, the outlet temperature is 100-130℃, the feeding speed of the peristaltic pump is 10-20r / min, and the nozzle rotation speed is 350r / min.

[0021] The application discloses a SiC@C-Si composite powder with core-shell structure for thermal spraying, which is prepared based on a preparation method thereof.

[0022] The present application has the following beneficial effects:

[0023] The SiC@C-Si composite powder for thermal spraying with a core-shell structure and the preparation method thereof have the following beneficial effects: in the specific operation, the SiC particles coated with polydopamine are mixed with Si, and then granulated to form the SiC@C-Si composite powder for thermal spraying with a core-shell structure, and then sprayed to form a modified SiC coating. On the one hand, the existence of the core-shell structure composite relieves the problem of serious oxidation and decomposition of SiC in the plasma jet; on the other hand, Si as the second heat protection after granulation relieves the thermal expansion mismatch with the C / C composite material by virtue of the advantages of high melting degree of Si in thermal spraying and the reaction of Si and C to generate SiC, which not only forms a liquid phase in the spraying process, is conducive to the melting and spreading of the coating on the substrate surface to form a dense coating, but also utilizes the reaction of Si with free C in the substrate and the coating in the heat treatment process to improve the bonding strength of the coating. In addition, it should be noted that Si can provide Si source for the formation of SiO2 glass film in the subsequent oxidation service process of the coating, fill the pores and defects in the coating, and further improve the oxygen resistance of the coating. At the same time, the preparation process of the present application is simple and controllable, has strong designability, low preparation cost and short cycle, is suitable for large-scale production of plasma sprayed SiC coating, and is also suitable for preparation of inorganic composite powder material with a core-shell structure, and has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 SEM and TEM morphologies of the original SiC particles and the SiC@PDA powder and corresponding EDS result graphs;

[0025] Figure 2 Surface element XPS analysis graphs of the SiC@PDA powder before and after heat treatment at 800 DEG C. DETAILED DESCRIPTION

[0026] In order to enable the personnel in the technical field to better understand the present application scheme, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments, and are not intended to limit the scope of the present application. In addition, in the following description, the description of the known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present application. Based on the embodiments in the present application, all other embodiments obtained by the ordinary skilled in the art without making creative efforts should belong to the scope of protection of the present application.

[0027] The structural schematic diagram according to the disclosed embodiment is shown in the accompanying drawings. The drawings are not drawn to scale, in which some details are exaggerated for the purpose of clarity and some details can be omitted. The shapes of various regions, layers and the relative size and position relationship therebetween shown in the drawings are only exemplary, and in actuality, can be deviated due to manufacturing tolerance or technical limitation, and the regions / layers with different shapes, sizes and relative positions can be additionally designed according to actual needs by those skilled in the art.

[0028] The preparation method of the SiC@C-Si composite powder with core-shell structure for thermal spraying according to the present application comprises the following steps:

[0029] 1) Dissolve tris(hydroxymethyl)aminomethane and SiC in deionized water, stir uniformly, adjust the pH value, and obtain a SiC uniformly dispersed solution;

[0030] 2) Add dopamine hydrochloride (PDA) to the SiC uniformly dispersed solution obtained in step 1), stir for 48 h, separate by suction filtration, dry the obtained product, and obtain SiC particles coated with polydopamine (SiC@PDA);

[0031] 3) Heat treat the SiC particles coated with polydopamine (SiC@PDA) obtained in step 2), and obtain SiC@C powder;

[0032] 4) Mix the SiC@C powder obtained in step 3) with Si to obtain a mixed powder, add the mixed powder, polyvinyl alcohol (PVA) solution, deionized water and anhydrous ethanol into a ball mill tank, and ball mill on a horizontal ball mill for 4-6 h to obtain a slurry suspension;

[0033] 5) Pump the slurry suspension obtained in step 4) into a spray granulation device through a peristaltic pump, use the centrifugal force generated by a high-speed rotating nozzle to atomize the slurry suspension into droplets, and make the droplets evaporate water by heat convection with high-temperature dry air to form SiC@C-Si composite powder (SiC@C-Si spherical granulation powder) with core-shell structure for thermal spraying.

[0034] In this embodiment, in step 1), the mass ratio of tris(hydroxymethyl)aminomethane to SiC is (2-3):96.

[0035] In this embodiment, in step 1), the pH value is adjusted to 9.5 by hydrochloric acid.

[0036] In this embodiment, in step 2), the mass ratio of dopamine hydrochloride to SiC in the SiC uniformly dispersed solution is (5-6):96, the temperature during drying is 80°C, and the drying time is 24 h.

[0037] In this embodiment, the operation process of step 3) is as follows:

[0038] The polydopamine-coated SiC particles (SiC@PDA) obtained in step 2) are heat-treated at 800-1000℃ under an argon atmosphere.

[0039] In this embodiment, in step 4), the mass ratio of the mixed powder, PVA solution, deionized water and anhydrous ethanol is (1-5):(1-5):1:1.

[0040] In this embodiment, in the granulation process of step 5), the inlet temperature is 300-350℃, the outlet temperature is 100-130℃, the feeding speed of the peristaltic pump is 10-20r / min, and the nozzle rotation speed is 350r / min.

[0041] The application discloses a SiC@C-Si composite powder with a core-shell structure for thermal spraying.

[0042] Example 1

[0043] This embodiment comprises the following steps:

[0044] 1) 48g of SiC powder is dispersed in 150ml of deionized water, 1.2g of tris(hydroxymethyl)aminomethane is added after uniform dispersion, hydrochloric acid is used to adjust the pH value to 9.5, then 2.5g of dopamine hydrochloride is added, and stirring is performed for 48h to obtain a SiC@PDA dispersion;

[0045] 2) The SiC@PDA dispersion obtained in step 1) is subjected to suction filtration separation, the obtained powder is washed with deionized water three times, and then washed with ethanol three times, and the washed solid is placed in a constant-temperature oven at 80℃ for drying for 24h to obtain a SiC@PDA solid powder;

[0046] 3) The SiC@PDA solid powder obtained in step 2) is placed in a tubular heat treatment furnace, heated to 800℃ at a heating rate of 5℃ / min under an argon atmosphere, and kept for 2h, and then cooled to room temperature at a cooling rate of 4℃ / min to obtain a carbonized SiC@C core-shell structure powder;

[0047] 4) The carbonized SiC@C core-shell structure powder obtained in step 3) is mixed with Si powder to obtain a mixed powder, the mixed powder, PVA solution, deionized water and anhydrous ethanol are weighed in a mass ratio of 4:4:1:1, and then transferred to a ball mill jar, and then ball-milled on a horizontal ball mill for 4-6h to obtain a uniformly mixed slurry suspension;

[0048] 5) The slurry suspension obtained in step 4) is sent into a spray granulation device by a peristaltic pump, the inlet temperature of the spray granulation device is controlled to be 320-350°C, the outlet temperature is controlled to be 100-120°C, the feeding speed of the peristaltic pump is set to be 15 r / min, the rotation speed of the spray head is controlled to be 350 r / min, and the spray granulation is sieved again to obtain the SiC@C-Si composite powder with core-shell structure for thermal spraying.

[0049] Example Two

[0050] The example includes the following steps:

[0051] 1) 48 g of SiC powder is dispersed in 150 ml of deionized water, 1.5 g of tris(hydroxymethyl) aminomethane is added after uniform dispersion, hydrochloric acid is used to adjust the pH value to 9.5, then 3 g of dopamine hydrochloride is added, and stirring is performed for 48 h to obtain a SiC@PDA dispersion;

[0052] 2) The SiC@PDA dispersion obtained in step 1) is subjected to suction filtration separation, the obtained powder is washed with deionized water three times, and then washed with ethanol three times, and the washed solid is placed in a constant temperature oven at 80°C for drying for 24 h to obtain a SiC@PDA solid powder;

[0053] 3) The SiC@PDA solid powder obtained in step 2) is placed in a tubular heat treatment furnace, heated to 900°C at a heating rate of 5°C / min under an argon atmosphere, and kept for 2 h, and then cooled to room temperature at a cooling rate of 4°C / min to obtain a carbonized SiC@C core-shell structure powder;

[0054] 4) The carbonized SiC@C core-shell structure powder obtained in step 3) is mixed with Si powder to obtain a mixed powder, the mixed powder, a PVA solution, deionized water, and anhydrous ethanol are weighed in a mass ratio of 4:4:1:1, and then transferred into a ball milling tank, and then ball milled on a horizontal ball mill for 4-6 h to obtain a uniformly mixed slurry suspension;

[0055] 5) The slurry suspension obtained in step 4) is sent into a spray granulation device by a peristaltic pump, the inlet temperature of the spray granulation device is controlled to be 320-350°C, the outlet temperature is controlled to be 100-120°C, the feeding speed of the peristaltic pump is set to be 15 r / min, the rotation speed of the spray head is controlled to be 350 r / min, and the spray granulation is sieved again to obtain the SiC@C-Si composite powder with core-shell structure for thermal spraying.

[0056] Example Three

[0057] The example includes the following steps:

[0058] 1) 48 g of SiC powder was dispersed in 150 ml of deionized water, 1.5 g of tris(hydroxymethyl) aminomethane was added after uniform dispersion, hydrochloric acid was used to adjust the pH value to 9.5, then 3 g of dopamine hydrochloride was added, and stirred for 48 h to obtain a SiC@PDA dispersion;

[0059] 2) The SiC@PDA dispersion obtained in step 1) was separated by suction filtration, the obtained powder was washed with deionized water three times, and then washed with ethanol three times, and the washed solid was placed in a constant temperature oven at 80°C for drying for 24 h to obtain a SiC@PDA solid powder;

[0060] 3) The SiC@PDA solid powder obtained in step 2) was placed in a tubular heat treatment furnace, heated to 1000°C at a heating rate of 5°C / min under an argon atmosphere, and kept for 2 h, and then cooled to room temperature at a cooling rate of 4°C / min to obtain a carbonized SiC@C core-shell structure powder;

[0061] 4) The carbonized SiC@C core-shell structure powder obtained in step 3) was mixed with Si powder to obtain a mixed powder, and the mixed powder, PVA solution, deionized water and anhydrous ethanol were weighed in a mass ratio of 4:4:1:1, then transferred to a ball mill jar, and then ball milled on a horizontal ball mill for 4-6 h to obtain a uniformly mixed slurry suspension;

[0062] 5) The slurry suspension obtained in step 4) was sent into a spray granulation device by a peristaltic pump, the inlet temperature of the spray granulation device was controlled at 320-350°C, the outlet temperature was controlled at 100-120°C, the feeding speed of the peristaltic pump was set at 15 r / min, and the rotation speed of the spray head was controlled at 350 r / min, and then sieved after spray granulation to obtain a SiC@C-Si composite powder with core-shell structure for thermal spraying.

[0063] Example Four

[0064] This example includes the following steps:

[0065] 1) 48 g of SiC powder was dispersed in 150 ml of deionized water, 0.5 g of tris(hydroxymethyl) aminomethane was added after uniform dispersion, hydrochloric acid was used to adjust the pH value to 9.5, then 1 g of dopamine hydrochloride was added, and stirred for 48 h to obtain a SiC@PDA dispersion;

[0066] 2) The SiC@PDA dispersion obtained in step 1) was separated by suction filtration, the obtained powder was washed with deionized water three times, and then washed with ethanol three times, and the washed solid was placed in a constant temperature oven at 80°C for drying for 24 h to obtain a SiC@PDA solid powder;

[0067] 3) The SiC@PDA solid powder obtained in step 2) is placed in a tube heat treatment furnace, heated to 500°C at a heating rate of 5°C / min under an argon atmosphere, and kept for 2h, and then cooled to room temperature at a cooling rate of 4°C / min, to obtain the carbonized SiC@C core-shell structure powder;

[0068] 4) The carbonized SiC@C core-shell structure powder obtained in step 3) is mixed with Si powder to obtain a mixed powder, and the mixed powder, PVA solution, deionized water and anhydrous ethanol are weighed in a mass ratio of 4:4:1:1, and then transferred to a ball mill jar, and then ball milled on a horizontal ball mill for 4-6h to obtain a uniformly mixed slurry suspension;

[0069] 5) The slurry suspension obtained in step 4) is sent into a spray granulation device by a peristaltic pump, the inlet temperature of the spray granulation device is controlled at 320-350°C, the outlet temperature is controlled at 100-120°C, the feeding speed of the peristaltic pump is set at 15r / min, and the spray head rotation speed is controlled at 350r / min, and then sieved again after spray granulation to obtain the SiC@C-Si composite powder with core-shell structure for thermal spraying.

[0070] Example Five

[0071] This example includes the following steps:

[0072] 1) 48g of SiC powder is dispersed in 150ml of deionized water, after uniform dispersion, 1.5g of tris(hydroxymethyl)aminomethane is added, the pH value is adjusted to 9.5 using hydrochloric acid, then 3g of hydrochloric acid dopamine is added, and stirred for 48h to obtain a SiC@PDA dispersion;

[0073] 2) The SiC@PDA dispersion obtained in step 1) is subjected to suction filtration separation, the obtained powder is washed with deionized water three times, and then washed with ethanol three times, and the washed solid is placed in a constant temperature oven at 80°C for drying for 24h to obtain a SiC@PDA solid powder;

[0074] 3) The SiC@PDA solid powder obtained in step 2) is placed in a tube heat treatment furnace, heated to 1500°C at a heating rate of 5°C / min under an argon atmosphere, and kept for 2h, and then cooled to room temperature at a cooling rate of 4°C / min, to obtain the carbonized SiC@C core-shell structure powder;

[0075] 4) The carbonized SiC@C core-shell structure powder obtained in step 3) is mixed with Si powder to obtain a mixed powder, and the mixed powder, PVA solution, deionized water and anhydrous ethanol are weighed in a mass ratio of 4:4:1:1, and then transferred to a ball mill jar, and then ball milled on a horizontal ball mill for 4-6h to obtain a uniformly mixed slurry suspension;

[0076] 5) The slurry suspension obtained in step 4) is pumped into a spray granulation device by a peristaltic pump, the inlet temperature of the spray granulation device is controlled to be 320-350℃, the outlet temperature is controlled to be 100-120℃, the feeding speed of the peristaltic pump is set to be 15r / min, the rotation speed of the spray head is controlled to be 350r / min, and the spray granulation is followed by sieving again to obtain the SiC@C-Si composite powder with core-shell structure for thermal spraying.

[0077] Example Six

[0078] The preparation method of the SiC@C-Si composite powder with core-shell structure for thermal spraying provided by the application comprises the following steps:

[0079] 1) Dissolve tris(hydroxymethyl)aminomethane and SiC in deionized water, stir uniformly, and adjust the pH value to obtain a SiC uniformly dispersed solution;

[0080] 2) Add dopamine hydrochloride (PDA) to the SiC uniformly dispersed solution obtained in step 1), stir for 48h, separate by suction filtration, and dry the obtained product to obtain polydopamine coated SiC particles (SiC@PDA);

[0081] 3) Heat treat the polydopamine coated SiC particles (SiC@PDA) obtained in step 2) to obtain SiC@C powder;

[0082] 4) Mix the SiC@C powder obtained in step 3) with Si to obtain mixed powder, and add the mixed powder, polyvinyl alcohol (PVA) solution, deionized water and anhydrous ethanol into a ball milling tank, and then ball mill on a horizontal ball mill for 4h to obtain a slurry suspension;

[0083] 5) The slurry suspension obtained in step 4) is pumped into a spray granulation device by a peristaltic pump, the inlet temperature of the spray granulation device is controlled to be 320-350℃, the outlet temperature is controlled to be 100-120℃, the feeding speed of the peristaltic pump is set to be 15r / min, the rotation speed of the spray head is controlled to be 350r / min, and the spray granulation is followed by sieving again to obtain the SiC@C-Si composite powder with core-shell structure for thermal spraying.

[0084] In this embodiment, in step 1), the mass ratio of tris(hydroxymethyl)aminomethane to SiC is 2:96.

[0085] In this embodiment, in step 1), the pH value is adjusted to 9.5 by hydrochloric acid.

[0086] In this embodiment, in step 2), the mass ratio of dopamine hydrochloride to SiC in the SiC uniformly dispersed solution is 5:96, the temperature during drying is 80℃, and the drying time is 24h.

[0087] In this embodiment, the operation process of step 3) is as follows:

[0088] The polydopamine-coated SiC particles (SiC@PDA) obtained in step 2) were heat-treated at 800°C under an argon atmosphere.

[0089] In this embodiment, in step 4), the mass ratio of the mixed powder, PVA solution, deionized water and anhydrous ethanol is 1:1:1:1.

[0090] In this embodiment, during the granulation process in step 5), the inlet temperature is 300°C, the outlet temperature is 100°C, the feeding speed of the peristaltic pump is 10 r / min, and the nozzle rotation speed is 350 r / min.

[0091] Example 7

[0092] The method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying according to the present invention includes the following steps:

[0093] 1) Dissolve tris(hydroxymethyl)aminomethane and SiC in deionized water, stir until homogeneous, and adjust the pH value to obtain a uniformly dispersed SiC solution;

[0094] 2) Add dopamine hydrochloride (PDA) to the uniformly dispersed SiC solution obtained in step 1), stir for 48 hours, filter and separate, and dry the obtained product to obtain polydopamine-coated SiC particles (SiC@PDA).

[0095] 3) The polydopamine-coated SiC particles (SiC@PDA) obtained in step 2) are subjected to heat treatment to obtain SiC@C powder;

[0096] 4) Mix the SiC@C powder obtained in step 3) with Si to obtain a mixed powder. Add the mixed powder, polyvinyl alcohol (PVA) solution, deionized water and anhydrous ethanol to a ball mill jar, and then ball mill on a horizontal ball mill for 6 hours to obtain a slurry suspension.

[0097] 5) The slurry suspension obtained in step 4) is fed into the spray granulation equipment by a peristaltic pump. The centrifugal force generated by the high-speed rotating nozzle is used to atomize the slurry suspension into droplets, and thermal convection occurs with the high-temperature dry air, causing the water in the droplets to evaporate and condense to form SiC@C-Si composite powder with core-shell structure (SiC@C-Si spherical granulation powder) for thermal spraying.

[0098] In this embodiment, in step 1), the mass ratio of tris(hydroxymethyl)aminomethane to SiC is 3:96.

[0099] In this embodiment, in step 1), the pH value is adjusted to 9.5 using hydrochloric acid.

[0100] In this embodiment, in step 2), the mass ratio of dopamine hydrochloride to SiC in the uniformly dispersed SiC solution is 6:96, the temperature during the drying process is 80°C, and the drying time is 24 hours.

[0101] In this embodiment, the operation process of step 3) is as follows:

[0102] The polydopamine-coated SiC particles (SiC@PDA) obtained in step 2) were heat-treated at 1000°C under an argon atmosphere.

[0103] In this embodiment, in step 4), the mass ratio of the mixed powder, PVA solution, deionized water and anhydrous ethanol is 5:5:1:1.

[0104] In this embodiment, during the granulation process in step 5), the inlet temperature is 350°C, the outlet temperature is 130°C, the feeding speed of the peristaltic pump is 20 r / min, and the nozzle rotation speed is 350 r / min.

[0105] Example 8

[0106] The method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying according to the present invention includes the following steps:

[0107] 1) Dissolve tris(hydroxymethyl)aminomethane and SiC in deionized water, stir until homogeneous, and adjust the pH value to obtain a uniformly dispersed SiC solution;

[0108] 2) Add dopamine hydrochloride (PDA) to the uniformly dispersed SiC solution obtained in step 1), stir for 48 hours, filter and separate, and dry the obtained product to obtain polydopamine-coated SiC particles (SiC@PDA).

[0109] 3) The polydopamine-coated SiC particles (SiC@PDA) obtained in step 2) are subjected to heat treatment to obtain SiC@C powder;

[0110] 4) Mix the SiC@C powder obtained in step 3) with Si to obtain a mixed powder. Add the mixed powder, polyvinyl alcohol (PVA) solution, deionized water and anhydrous ethanol into a ball mill jar, and then ball mill on a horizontal ball mill for 5 hours to obtain a slurry suspension.

[0111] 5) The slurry suspension obtained in step 4) is fed into the spray granulation equipment by a peristaltic pump. The centrifugal force generated by the high-speed rotating nozzle is used to atomize the slurry suspension into droplets, and thermal convection occurs with the high-temperature dry air, causing the water in the droplets to evaporate and condense to form SiC@C-Si composite powder with core-shell structure (SiC@C-Si spherical granulation powder) for thermal spraying.

[0112] In this embodiment, in step 1), the mass ratio of tris(hydroxymethyl)aminomethane to SiC is 2.5:96.

[0113] In this embodiment, in step 1), the pH value is adjusted to 9.5 using hydrochloric acid.

[0114] In this embodiment, in step 2), the mass ratio of dopamine hydrochloride to SiC in the uniformly dispersed SiC solution is 5.5:96, the temperature during the drying process is 80°C, and the drying time is 24 hours.

[0115] In this embodiment, the operation process of step 3) is as follows:

[0116] The polydopamine-coated SiC particles (SiC@PDA) obtained in step 2) were heat-treated at 900°C under an argon atmosphere.

[0117] In this embodiment, in step 4), the mass ratio of the mixed powder, PVA solution, deionized water and anhydrous ethanol is 3:3:1:1.

[0118] In this embodiment, during the granulation process in step 5), the inlet temperature is 320°C, the outlet temperature is 120°C, the feeding speed of the peristaltic pump is 15 r / min, and the nozzle rotation speed is 350 r / min.

[0119] Comparative Example 1

[0120] This comparative example includes the following steps:

[0121] 1) Mix 48g of SiC powder with Si and C powder to form a mixed powder, and weigh it with PVA solution, deionized water and anhydrous ethanol in a mass ratio of 4:4:1:1. Then transfer it to a ball mill jar and ball mill it on a horizontal ball mill for 4-6 hours to form a uniform slurry suspension.

[0122] 2) The suspension slurry solution obtained in step 1) is fed into the nozzle of the spray granulation equipment through a peristaltic pump. The inlet temperature is controlled at 320-350℃ and the outlet temperature is controlled at 100-120℃. The feeding speed of the peristaltic pump is set to 15r / min and the nozzle rotation speed is controlled at 350r / min. After spray granulation, it is sieved again to obtain SiC-Si-C powder that can be used for thermal spraying.

[0123] Figure 1 SEM and TEM morphology of the original SiC particles (a) and SiC@PDA powder (bd), and corresponding EDS results. Figure 1 As can be seen, polydopamine coating has a good effect, with a film-like coating on the surface. Line scan results show that the SiC particles have a shell rich in C and N elements.

[0124] Figure 2 Here are the XPS analysis images of the surface elements of SiC@PDA powder before and after heat treatment at 800℃. Figure 2 As can be seen, the oxygen content on the powder surface is significantly reduced after heat treatment, which means that the organic byproducts generated during dopamine polymerization are degraded and disappear after heat treatment, which is beneficial to subsequent plasma spraying. In addition, the enhanced C peak means the formation of a carbon shell on the powder surface, which can be used for subsequent granulation spraying.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying, characterized in that, include: 1) Heat-treat polydopamine-coated SiC particles to obtain SiC@C powder; 2) Mix the SiC@C powder obtained in step 1) with Si to obtain a mixed powder. Mix the mixed powder with polyvinyl alcohol solution, deionized water and anhydrous ethanol and then ball mill to obtain a slurry suspension. 3) Spray granulation is performed on the slurry suspension obtained in step 2) to obtain SiC@C-Si composite powder with core-shell structure for thermal spraying.

2. The method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying according to claim 1, characterized in that, Step 3) is as follows: The slurry suspension obtained in step 2) is fed into a spray granulation device by a peristaltic pump. The centrifugal force generated by the rotating nozzle atomizes the slurry suspension into droplets, and thermal convection occurs with the high-temperature dry air, causing the water in the droplets to evaporate and condense to form SiC@C-Si composite powder with a core-shell structure for thermal spraying.

3. The method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying according to claim 1, characterized in that, Step 1) also includes: 11) Dissolve tris(hydroxymethyl)aminomethane and SiC in deionized water, stir until homogeneous, and adjust the pH value to obtain a uniformly dispersed SiC solution; 12) Add dopamine hydrochloride to the uniformly dispersed SiC solution obtained in step 1), stir, filter and separate, and dry the obtained product to obtain polydopamine-coated SiC particles.

4. The method for preparing core-shell structured SiC@C-Si composite powder for thermal spraying according to claim 3, characterized in that, In step 11), the mass ratio of tris(hydroxymethyl)aminomethane to SiC is (2-3):

96.

5. The method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying according to claim 3, characterized in that, In step 11), the pH value is adjusted to 9.5 using hydrochloric acid.

6. The method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying according to claim 3, characterized in that, In step 12), the mass ratio of dopamine hydrochloride to SiC in the uniformly dispersed SiC solution is (5-6):

96.

7. The method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying according to claim 1, characterized in that, The operation process of step 1) is as follows: The polydopamine-coated SiC particles obtained in step 2) were heat-treated at 800–1000 °C under an argon atmosphere.

8. The method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying according to claim 1, characterized in that, In step 2), the mass ratio of the mixed powder, PVA solution, deionized water and anhydrous ethanol is (1-5):(1-5):1:

1.

9. The method for preparing SiC@C-Si composite powder with a core-shell structure for thermal spraying according to claim 2, characterized in that, In step 3), the spray granulation process has an inlet temperature of 300℃-350℃, an outlet temperature of 100℃-130℃, a peristaltic pump feed rate of 10r / min-20r / min, and a nozzle rotation speed of 350r / min.

10. A SiC@C-Si composite powder with a core-shell structure for thermal spraying, characterized in that, It is prepared according to the preparation method of SiC@C-Si composite powder with core-shell structure for thermal spraying as described in any one of claims 1-9.

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