CN112415644A

CN112415644A - Ultra-light C/C-SiC space reflector and preparation method and application thereof

Info

Publication number: CN112415644A
Application number: CN202011329563.7A
Authority: CN
Inventors: 强新发; 巴志新; 张保森; 巨佳; 李旋
Original assignee: Nanjing Institute of Technology
Current assignee: Nanjing Institute of Technology
Priority date: 2020-11-24
Filing date: 2020-11-24
Publication date: 2021-02-26
Anticipated expiration: 2040-11-24
Also published as: CN112415644B

Abstract

The invention discloses an ultra-lightweight C/C-SiC space reflector, which comprises a C/C composite material, a SiC gradient transition layer embedded on the surface of the C/C composite material, and a graphene-SiCNWs multidimensional hybridization enhanced CVD-SiC coating arranged on the surface of the SiC gradient transition layer. The invention also discloses an application of the preparation method of the ultra-lightweight C/C-SiC space reflector. According to the invention, the PC-SiC transition coating is prepared on the surface of the ultralight C/C composite material, so that the thermal stress generated by the thermal expansion mismatch of the mirror CVD-SiC coating and the C/C matrix is reduced, and the graphene-wound SiC nanowire reinforcement is grown on the surface of the embedded SiC coating by a one-step CVD method, so that the interface combination between the SiCNWs and the CVD-SiC matrix is improved, and the effect of enhancing the CVD-SiC optical coating by the single SiCNWs is improved by virtue of the excellent mechanical property of the graphene.

Description

Ultra-light C/C-SiC space reflector and preparation method and application thereof

Technical Field

The invention relates to an ultra-lightweight C/C-SiC space reflector and a preparation method and application thereof, belonging to the technical field of chemical materials.

Background

The space camera as the 'eye' of the space vehicle has important significance in the aerospace field, and countries in the world also have fierce competition in the field.

And with the development of space application technology, higher and higher requirements are put on the emission load and the resolution of the space camera. In order to further reduce the emission cost and improve the resolution of the space camera, new optical reflectors are gradually developed in the direction of large caliber and light weight.

Space optical remote sensing systems such as space telescopes, remote sensing reconnaissance cameras and the like have important scientific and military significance in the fields of earth observation, space exploration and the like, are one of the key points of current international space technical research, and are important embodiment of comprehensive national force. With the continuous improvement of the requirement on the detection precision, the resolution requirement of the space optical remote sensing system is higher and higher.

Since Galileo invented astronomical telescope in 1609 years, the observation capability of the optical system is continuously improved, and a key, namely the aperture of the reflector, is not separated. For an optical imaging system with a mirror aperture of D, the angular resolution alpha is 1.22 lambda/D. It can be seen that the larger the mirror aperture, the higher the resolution and accuracy of the optical telescope, especially for moving objects. Therefore, the demand for larger aperture mirrors is endless and is the focus of international competition. However, as the aperture of the reflector is increased, the self weight of the reflector is greatly increased, and the emission cost is increased; meanwhile, the deformation tendency caused by the change of the environmental temperature is more serious, and the deformation reaches the micron level, which causes image deformation or imaging failure. From this, it can be seen that if the resolution of the space optical remote sensing system is improved by increasing the aperture of the mirror, the requirements for weight reduction and stability of the mirror become more severe.

The reflecting mirror, which is a key component in the above-mentioned space optical system, must satisfy requirements such as light weight, high specific stiffness, and good thermal stability. At present, single optical glass, metal and SiC ceramic as traditional reflector materials are difficult to meet the requirements of large-caliber ultra-light weight and stability due to performance limitation, so that development of new materials meeting development requirements of reflectors and having excellent comprehensive performance becomes a key point of research of space optical remote sensing systems.

Mirror material development to date has shifted from single glass, metal and SiC ceramics to carbon fiber composites. The carbon fiber composite material has the advantages of light weight, high specific strength, high specific modulus, low thermal expansion coefficient and good performance designability, and has become the first choice of the mirror surface material of the next generation of space telescope.

The carbon fiber reinforced composite material has the advantages of low density, high specific stiffness, small thermal expansion coefficient, high thermal stability and the like, and thus becomes a hot material for competitive research in the field of reflectors in recent years. Particularly, in the research on the C/SiC (carbon fiber reinforced silicon carbide ceramic) composite material, due to the addition of the carbon fibers, the toughness of the SiC ceramic is improved, the sensitivity of the SiC ceramic to cracks and thermal shock is effectively overcome, the SiC ceramic is easier to machine, and the SiC ceramic is suitable for large-size integral molding and is widely researched in recent years. Countries such as the united states, france, russia, japan, germany, etc. have conducted extensive research on C/SiC composites and have come out high performance products of different dimensional specifications and surface types. The SPICA space astronomical telescope with the caliber of 3.5 meters, which is supposed to be emitted after 2020 in Japan, takes the C/SiC composite material as one of candidate materials for the integrally-formed main reflecting mirror. In China, Wuhan university of science and technology takes the first time to carry out the systematic research of the C/SiC composite material reflector, and obtains better research results on the manufacturing process. In 2018, a C/SiC composite material reflector with the caliber of 4 meters is successfully developed by Changchun optical machine, and the reflector is also a maximum-caliber high-precision silicon carbide aspheric reflector which is published and reported internationally at present, but the successful application of the reflector is not reported at present. The carbon fiber reinforced carbon matrix composite (C/C composite) is an important member in the carbon fiber reinforced composite, and compared with the C/SiC composite, the carbon fiber reinforced carbon matrix composite has the advantages of lower density, higher specific stiffness, smaller thermal expansion coefficient and even zero expansion; the C/C composite material is completely composed of single C element, the difference between the fiber and the matrix is smaller, and the isotropy is better; the element C has higher stability, so that the C/C composite material has good radiation resistance, acid and alkali corrosion resistance; in addition, compared with a resin-based composite material, the C/C composite material has no problems of moisture absorption expansion, decomposition in a severe space environment, air release and the like. Therefore, the C/C composite material has a very good application prospect as a space reflector material.

Related research on C/C composite material reflectors is firstly carried out by Meyers and the like in the United states, a C/C composite material is taken as a substrate, a SiC coating is prepared on the surface of the C/C composite material by adopting a chemical vapor reaction or radio frequency sputtering method, and the surface part of the SiC coating is converted into SiO by high-temperature oxidation₂Then radio frequency sputtering is adopted to SiO₂Preparing a glass layer on the surface of the layer, and finally carrying out optical polishing on the glass layer to obtain the mirror surface. However, the preparation process is quite complex and high in cost, the glass layer can obviously increase the weight of the material, the advantage of light weight of the C/C composite material is reduced, and the interlayer glass can be used as a heat insulation barrier between the outer layer optical glass and the substrate, so that the coating is layered. In order to overcome the defects of glass coatings, J.Shipley and the like prepare a plurality of metal layers on the surface of a C/C composite material, wherein the metal layers are respectively Cr/Au (Cu)/Ni/Ag (Al) from inside to outside, the interlayer bonding force between the metal layers is strong, the heat conductivity coefficient is high, the interlayer stress can be reduced, and the same plurality of metal layers are prepared on the reverse side so as to ensure the integral heat balance of the reflector and prevent the delamination phenomenon. However, the structure is still complex and is easy to deform due to the double-metal-layer effect. Recently, d.e.krumweide et al have also conducted studies on C/C composite mirrors, which they believe are the only materials that can replace metallic beryllium mirrors and can be used in both humid and nuclear radiation environments. Firstly, preparing a C/C composite material blank by adopting a process method of carbon cloth dipping and layering, curing and carbonizing and chemical vapor infiltration, and then preparing a SiOx mirror reflection layer to finally obtain the C/C composite material reflector with higher surface type precision. However, SiOx coating is expensive to produce and difficult to mirror finish. H.Takeya, Mitsubishi corporation, takes a C/C composite material as a substrate, adopts a chemical plating method to prepare a metal Ni layer on the surface of the C/C composite material, and obtains the C/C composite material after optical polishingThe final profile accuracy is low, only 0.175 λ (λ 630 nm). Most researches on C/C composite materials in space optical remote sensing systems in other countries are concentrated on structural parts such as external lens barrels, main mirror substrates and secondary mirror tripods. The domestic research in the field of C/C composite material reflectors is still in the primary stage, and few researches on the technology of obtaining coatings with high bonding strength, good thermal stability and excellent optical performance on the surfaces of C/C composite materials are carried out, and few literature reports exist.

However, the C/C composite material has the characteristics of large surface roughness caused by the porosity and the fibers, and the like, so that the reflecting mirror surface is difficult to directly obtain through optical polishing. Therefore, the invention obtains the ultra-light C/C-SiC composite material reflector by preparing the novel SiC mirror surface coating on the surface of the C/C composite material, and further improves the international competitiveness of China in the field of reflectors.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides the ultra-light weight C/C-SiC space reflector which is prepared by adopting C/C composite materials with low density and the like.

Meanwhile, the invention provides a preparation method of the ultralight C/C-SiC space reflector, the method reduces the thermal stress generated by the mismatch of the thermal expansion of the mirror CVD-SiC and the C/C matrix by preparing the PC-SiC transition coating on the surface of the ultralight C/C composite material, and the graphene-SiCNWs is grown on the surface of the PC-SiC coating by one-step CVD method to wind the SiCNWs, so that the graphene-SiCNWs multidimensional hybrid nano reinforcement is constructed, the interface combination between the SiCNWs and the CVD-SiC matrix is improved, and the effect of the single SiCNWs on enhancing the CVD-SiC optical coating matrix is improved by virtue of the excellent mechanical property of the graphene.

Meanwhile, the invention provides an application of the ultra-lightweight C/C-SiC space reflector in a space optical remote sensing system.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

an ultra-lightweight C/C-SiC space reflector comprises a C/C composite material, a SiC gradient transition layer embedded on the surface of the C/C composite material, and a graphene-SiCNWs multidimensional hybridization enhanced CVD-SiC coating arranged on the surface of the SiC gradient transition layer; the SiC gradient transition layer is abbreviated as PC-SiC, the graphene-SiCNWs multidimensional hybridization enhanced CVD-SiC coating is abbreviated as G-SiCNWs-SiC, the graphene is abbreviated as G, and the SiCNWs are SiC nanowires.

The content of silicon element in the SiC gradient transition layer is gradually increased from the inside of the C/C composite material to the outer surface of the G-SiCNWs-SiC.

A preparation method of an ultra-lightweight C/C-SiC space reflector comprises the following steps:

s1, controllably preparing the SiC gradient transition layer by an embedding method:

embedding a sample of the C/C composite material into mixed powder, wherein the mixed powder comprises C powder, Si powder, a penetration enhancer and a ferrocene modifier; the mass ratio of the C powder to the Si powder is (2-3): 1, the penetration enhancer accounts for 5-10% of the mixed powder, and the ferrocene modifier accounts for 5-10% of the mixed powder; after embedding, heating and reacting for 2-3h at 2100-2300 ℃ to obtain a SiC gradient transition layer with a uniform tissue structure, namely PC-SiC;

s2, preparing G-SiCNWs on the surface of PC-SiC in a controllable way:

placing PC-SiC in a reaction zone in a CVD furnace, vacuumizing, and introducing H₂And Ar, when the temperature of the reaction zone reaches the deposition temperature of 1000-1200 ℃, the carrier gas H is opened₂In the presence of CH₃SiCl₃Introducing H into the bubbling bottle₂Is prepared from CH₃SiCl₃The mixture is taken into a furnace, the pressure and the air flow in the furnace are adjusted, the deposition pressure is 2000 and 5000Pa, and the deposition time is 1-4 h; CH (CH)₃SiCl₃The mole ratio of the intermediate C, Si is 1: (1-4); after the reaction, generating a G-SiCNWs multidimensional hybridization reinforcement on the surface of the PC-SiC;

s3, preparation of G-SiCNWs enhanced CVD-SiC mirror coating, namely G-SiCNWs-SiC:

directly adjusting CH in a CVD furnace without taking out a sample₃SiCl₃-H₂Carrying out CVD-SiC coating deposition to obtain a G-SiCNWs toughened CVD-SiC optical coating, namely G-SiCNWs-SiC;

and S4, optically processing the reflector to obtain the ultra-lightweight C/C-SiC space reflector.

The penetration enhancer comprises Al₂O₃、B₂O₃Or MgO.

In S2, the flow rate is CH₃SiCl₃And H₂In a molar ratio of 1: (1-4).

In S3, the process parameters include: deposition temperature: 1000-1150 degrees; the deposition time is 4-6 hours; deposition pressure: 1000-5000 Pa; gas flow rate: carrier gas hydrogen gas: 50-150 mL/min; reaction hydrogen: 2-4L/min; diluting argon gas: 1-2L/min; CH (CH)₃SiCl₃：5-10g/min。

An application of an ultra-lightweight C/C-SiC space reflector in a space optical remote sensing system.

The space optical remote sensing system comprises a space telescope or a remote sensing investigation camera.

The invention summarizes the research and development experience of the space reflector and combines the development trend of ultra-lightness and low cost of the future reflector, and the C/C composite material surface coating for the reflector is considered to meet the following requirements: has a coefficient of thermal expansion similar to that of the C/C matrix; the heat conductivity coefficient is high; the interface bonding force is stronger; the mirror surface optical performance is excellent. The SiC (CVD-SiC) coating prepared by the chemical vapor deposition method has been widely applied to the surface modification coating of the SiC ceramic substrate reflector due to the characteristics of high purity, good compactness, good chemical stability, good thermal conductivity, high specific stiffness, excellent polishing performance and the like. The CVD-SiC is widely researched as the anti-oxidation coating of the C/C composite material at home and abroad, and the comprehensive research results show that the thermal expansion coefficient mismatch and the weak bonding force of the CVD-SiC and the C/C composite material become the main reasons for causing the coating failure. The CVD-SiC coating is directly used as a mirror coating of the C/C composite material for the reflector, and a few documents are reported. The requirements in connection with the surface coating of C/C composites for reflectors are inferred to be two reasons: one is that CVD-SiC has large brittleness and large difference between thermal expansion coefficient and C/C matrix (alpha)_SiC≈4.5×10^-6 K^-1，α_C/C≈1.0×10^-6K^-1) In the preparation of CVD-SiCWhen the coating is coated, the coating has large residual stress, so that the CVD-SiC coating is cracked and even peeled off, and the quality of the optical coating is seriously influenced; and secondly, the interface bonding force is not high due to the mismatch of the thermal expansion coefficients, and the compact optical coating on the surface of the reflector has higher bonding force with the substrate, so as to ensure that the compact optical coating can bear the stress in the grinding and polishing processes during optical processing and the stress caused by thermal shock in the actual use process. Therefore, the key problems of limiting the application of the CVD-SiC coating as a mirror coating on the surface of the C/C composite material are that the CVD-SiC coating has high brittleness, weak bonding force with a C/C substrate, easy cracking of the coating caused by the brittleness, poor optical processing performance and the like.

In summary, the present invention develops high quality SiC mirror coatings in two ways:

1. self-strength and toughness of the coating: graphene grows on the surface of SiCNWs, and a 'graphene-SiCNWs' multidimensional hybridization nano reinforcement is constructed, so that the interface combination between the SiCNWs and a CVD-SiC matrix can be improved, and the CVD-SiC matrix can be enhanced by virtue of excellent mechanical properties of the graphene.

2. Reducing thermal stress due to thermal expansion mismatch: the embedded SiC coating is used as a transition layer of the C/C composite material antioxidant ceramic coating, so that the thermal expansion adaptation between the embedded SiC coating and the C/C composite material antioxidant ceramic coating is relieved, and the antioxidant and thermal shock resistance of the embedded SiC coating is improved. Therefore, the SiC gradient transition layer is prepared between the nano toughened CVD-SiC coating and the C/C substrate, a coating system with gradually increased thermal expansion coefficient is constructed, and the thermal stress between the coating and the substrate is relieved.

Namely, firstly preparing a SiC gradient transition layer (PC-SiC) on the surface of a C/C composite material meeting the requirement of mechanical property by adopting an embedding method, and then using trichloromethylsilane (CH)₃SiCl₃-H₂-Ar) is used as a reaction system, a CVD method is adopted to codeposit and grow a graphene-SiCNWs multidimensional hybridization reinforcement body on the surface of a PC-SiC coating in one step, then CVD process parameters are changed to directly deposit a CVD-SiC coating substrate to obtain a graphene-SiCNWs multidimensional hybridization reinforced CVD-SiC coating (G-SiCNWs-SiC), so that an optical SiC coating system with gradient change of thermal expansion coefficient and excellent toughness is constructed, and finally, optical polishing is carried out to obtain the ultra-light C/C-SiC reflection reinforcement bodyA mirror.

The invention has the following beneficial effects:

1. the reflector adopts a double-layer structure design, namely a SiC gradient transition layer (PC-SiC) and a graphene-SiCNWs multidimensional hybrid enhanced CVD-SiC coating (G-SiCNWs-SiC), and the double coating solves the problems of ultra-light weight, adaptive thermal expansion coefficient, improvement of SiCNWs brittle fracture caused by strong interface combination and the like.

2. According to the preparation process of the PC-SiC coating, particularly the addition of the ferrocene modifier can reduce the grain size, reduce the cracks of the PC-SiC coating and improve the uniformity of the PC-SiC coating, so that the quality of a transition layer is better.

And 3, preparing the graphene-modified SiC nanowire reinforcement on the surface of the PC-SiC coating by a one-step CVD method, so that the strong interface combination between the SiC nanowire and the SiC coating can be improved, and the quality of the CVD-SiC optical coating is improved.

4. According to the invention, the thermal stress generated by the thermal expansion mismatch of the mirror CVD-SiC and the C/C matrix is reduced by preparing the PC-SiC transition coating on the surface of the ultralight C/C composite material. The embedded silicon carbide coating (PC-SiC) is in gradient distribution on the surface of the C/C composite material (namely, the content of silicon element is gradually increased from the inside of the matrix to the outermost surface), so that the thermal expansion coefficient is in gradient distribution from the C/C matrix to the PC-SiC surface layer, and the thermal expansion mismatch is relieved. And because of the addition of the ferrocene modifier, the grain size is reduced, and the cracks of the PC-SiC coating are reduced.

The addition of the SiC nanowires (SiCNWs) can obviously improve the bonding strength of the CVD-SiC coating and the C/C matrix, and simultaneously improve the strength and toughness of the coating. However, the SiCNWs and the CVD-SiC matrix are in strong interface combination, which is not beneficial to the release of thermal stress in the cooling process after the deposition of the coating is finished, and the brittle fracture of the SiCNWs is caused, so that the coating is cracked. Therefore, weakening the interface bonding of the SiCNWs and the CVD-SiC coating matrix is the key for improving the toughness of the coating, but the toughness and the strength are usually a pair of spears, and a new problem is faced in how to ensure that the weakened interface bonding improves the toughness of the coating and simultaneously ensure that the strength of the coating is not lost. Graphene (graphene) is a two-dimensional material formed by hybridization of carbon atoms through sp2, and has an ultra-large specific surface area (2630 m)²Perg), ultrahigh strength (up to 130GPa), ultrahigh chemical stability, and ultralight specific gravity, and is known as the strongest material. In recent years, related studies of graphene composites have demonstrated the great potential of graphene as reinforcement. Therefore, the graphene-wound SiCNWs are grown on the surface of the PC-SiC coating by a one-step CVD method, and the graphene-SiCNWs multidimensional hybrid nano reinforcement is constructed, so that the interface combination between the SiCNWs and the CVD-SiC matrix is improved, and the effect of reinforcing the CVD-SiC optical coating matrix by the single SiCNWs is improved by virtue of the excellent mechanical property of the graphene.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a surface SEM photograph of an embedding method for preparing a SiC gradient transition layer according to the present invention, wherein (a) ferrocene is not added; (b) adding ferrocene for modification;

FIG. 3 is a cross-sectional SEM photograph and an EDS line scan of a SiC gradient transition layer of the present invention;

FIG. 4 is an SEM photograph of a multi-dimensional hybrid reinforcement of G-SiCNWs of the present invention;

FIG. 5 is a picture of a mirror prepared in accordance with the present invention and a result of an optical property test;

FIG. 6 is a thermal shock weight loss curve from room temperature to 1400 ℃ for pure CVD-SiC and G-SiCNW-SiC coated samples of the present invention;

FIG. 7 is a graph of thermal shock results for pure CVD-SiC and G-SiCNW-SiC coated samples of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are merely illustrative of the invention and are not intended to be limiting.

Example 1:

as shown in fig. 1, the embodiment discloses an ultra-lightweight C/C-SiC space mirror, which includes a C/C composite material, a SiC gradient transition layer embedded in the surface of the C/C composite material, and a graphene-SiCNWs multi-dimensional hybrid enhanced CVD-SiC coating layer disposed on the surface of the SiC gradient transition layer; the SiC gradient transition layer is abbreviated as PC-SiC, the graphene-SiCNWs multidimensional hybridization enhanced CVD-SiC coating is abbreviated as G-SiCNWs-SiC, the graphene is abbreviated as G, and the SiCNWs are SiC nanowires.

The embodiment also discloses a preparation method of the ultra-lightweight C/C-SiC space reflector, which comprises the following steps:

(1) controllable preparation of SiC gradient transition layer by embedding method

C powder and Si powder are used as main raw materials, and a small amount of Al is added₂O₃The penetration enhancer and the ferrocene modifier are mixed powder, and the SiC gradient transition layer is prepared on the surface of the C/C composite material by adopting an embedding method. The technological parameters are as follows: carbon to silicon ratio (2-3): 1, temperature 2100-₂O₃The penetration enhancer is added in an amount of 5 mass percent and 5-10 mass percent of the modifier ferrocene, and the SiC gradient transition layer with uniform tissue structure, namely the PC-SiC coating, is obtained. The C/C composite material sample is embedded into the mixed powder by an embedding method, and the mixed powder and the surface of the C/C composite material are reacted.

As shown in fig. 2, the embedding method produces a surface SEM photograph of the SiC gradient transition layer, wherein (a) ferrocene is not added; (b) adding ferrocene for modification; as can be seen from the figure, the surface of the SiC gradient transition layer modified by adding the ferrocene has reduced cracks and reduced crack size, and the crystal grains are also finer. Therefore, in the embodiment, the addition of the ferrocene modifier can reduce the grain size, thereby reducing the cracks of the PC-SiC coating and improving the uniformity of the coating.

As shown in FIG. 3, a SEM and EDS line scan of the section of the SiC gradient transition layer is shown, in which a gradient distribution of Si from the C/C composite material matrix to the outer surface is clearly seen. Namely: the content of silicon element in the SiC gradient transition layer is gradually increased from the inside of the C/C composite material to the outer surface of the G-SiCNWs-SiC.

(2) Controllable preparation of G-SiCNWs multi-dimensional hybrid reinforcement on surface of PC-SiC coating

By CH₃SiCl₃-H₂And (4) preparing a G-SiCNWs multidimensional hybrid reinforcement on the surface of the PC-SiC coating by a Chemical Vapor Deposition (CVD) method through an-Ar reaction system. Wherein, CH₃SiCl₃Is not only a C sourceIs also a source of Si and has a C, Si molar ratio of 1, H₂As carrier gas and reducing gas, and Ar as diluent gas. Firstly, a matrix material (namely a C/C composite material with PC-SiC loaded on the surface) is placed in a reaction zone in a CVD furnace, and H is introduced after vacuum pumping₂And Ar, after the reaction zone temperature reaches the specified reaction temperature, the carrier gas H is opened₂Regulating the pressure and the air flow in the furnace, wherein the air flow is CH₃SiCl₃And H₂In a molar ratio of 1: (1-4), the precursor is subjected to complex chemical reaction in a furnace to generate G-SiCNWs. The technological parameters are as follows: the deposition temperature (1000-. In the embodiment, the G-SiCNWs is prepared under the condition that the surface of the SiC-embedded C/C composite material is free of a catalyst, and the graphene-coated SiC nanowires can be prepared in one step by controlling process parameters, particularly pressure and C/H ratio.

As shown in FIG. 4, which is an SEM photograph of the multi-dimensional hybrid reinforcement of G-SiCNWs of this example, it can be seen from FIG. 4 that the multi-dimensional hybrid reinforcement of G-SiCNWs was obtained in this example.

(3) Preparation of G-SiCNWs enhanced CVD-SiC mirror coating

And directly adjusting process parameters to deposit a CVD-SiC coating matrix under the state that a sample is not taken out, and densifying the G-SiCNWs porous strong and tough framework preform to prepare the G-SiCNWs toughened CVD-SiC optical coating. In this step, the process parameters include: deposition temperature: 1000-1150 degrees; the deposition time is 4-6 hours; deposition pressure: 1000-000 Pa; gas flow rate: carrier gas hydrogen gas: 50-150 mL/min; reaction hydrogen: 2-4L/min; diluting argon gas: 1-2L/min; CH (CH)₃SiCl₃: 5-10 g/min. And obtaining the ultra-lightweight C/C-SiC reflector after optical processing.

FIG. 5 shows the results of the ultra lightweight C/C-SiC mirror and the optical performance test of this embodiment.

The ultra-lightweight C/C-SiC reflector prepared by the embodiment has the advantages that the problems of cracks, peeling and the like cannot occur in the stress in the grinding and polishing process during optical processing and the stress caused by thermal shock in the actual use process.

The stress is not directly measured and can be reflected by other data, such as improved fracture toughness of the coating, reduced crack size, and superior thermal shock performance compared to SiC coatings without the addition of the reinforcing phase.

As shown in Table 1, the enhanced SiC coatings all had better hardness, modulus, and fracture toughness than the unreinforced pure CVD-SiC coating.

TABLE 1 hardness, modulus of elasticity and fracture toughness of reinforced and unreinforced SiC coatings

As shown in FIG. 6, the thermal shock weight loss curves from room temperature to 1400 ℃ for the pure CVD-SiC and G-SiCNW-SiC coated samples. As can be seen from the figure, the weight loss of the pure CVD-SiC coating sample after 30 times of thermal shock is as high as 6.2%, while the weight loss of the G-SiCNW-SiC coating sample after 30 times of thermal shock is only 2.5%, so the addition of the G-SiCNWs can obviously improve the thermal shock resistance of the SiC coating.

As shown in fig. 7, spallation and cracking of the pure CVD coating (left) occurred after thermal shock, while the reinforcement coating of the invention (right) did not.

Example 2:

embedding a sample of the C/C composite material into mixed powder, wherein the mixed powder comprises C powderSi powder, B₂O₃Penetration enhancer and ferrocene modifier; the mass ratio of the C powder to the Si powder is 2:1, the penetration enhancer accounts for 10% of the mixed powder, and the ferrocene modifier accounts for 5% of the mixed powder; after embedding, heating and reacting for 2h at 2100 ℃ to obtain a SiC gradient transition layer with a uniform tissue structure, namely PC-SiC;

s2, preparing G-SiCNWs on the surface of PC-SiC in a controllable way:

placing PC-SiC in a reaction zone in a CVD furnace, vacuumizing, and introducing H₂And Ar, when the temperature of the reaction zone reaches the deposition temperature of 1000 ℃, the carrier gas H is turned on₂In the presence of CH₃SiCl₃Introducing H into the bubbling bottle₂Is prepared from CH₃SiCl₃The mixture is carried into a furnace, the pressure and the air flow in the furnace are adjusted, the deposition pressure is 2000Pa, and the deposition time is 1 h; CH (CH)₃SiCl₃The mole ratio of the intermediate C, Si is 1: 2; after the reaction, generating a G-SiCNWs multidimensional hybridization reinforcement on the surface of the PC-SiC;

directly adjusting CH in a CVD furnace without taking out a sample₃SiCl₃-H₂-process parameters of the Ar reaction system, the process parameters comprising: deposition temperature: 1000 degrees; the deposition time is 4 hours; deposition pressure: 1000 Pa; gas flow rate: carrier gas hydrogen gas: 50 mL/min; reaction hydrogen: 2L/min; diluting argon gas: 1L/min; CH (CH)₃SiCl₃: 5 g/min; carrying out CVD-SiC coating deposition to obtain a G-SiCNWs toughened CVD-SiC optical coating, namely G-SiCNWs-SiC;

Example 3:

this example differs from example 2 only in that:

embedding a sample of the C/C composite material into mixed powder, wherein the mixed powder comprises C powder, Si powder, MgO penetration enhancer and ferrocene modifier; the mass ratio of the C powder to the Si powder is 3:1, the MgO penetration enhancer accounts for 8% of the mixed powder, and the ferrocene modifier accounts for 10% of the mixed powder; after embedding, heating and reacting for 3h at 2300 ℃ to obtain a SiC gradient transition layer with uniform tissue structure, namely PC-SiC;

s2, preparing G-SiCNWs on the surface of PC-SiC in a controllable way:

placing PC-SiC in a reaction zone in a CVD furnace, vacuumizing, and introducing H₂And Ar, when the temperature of the reaction zone reaches the deposition temperature of 1200 ℃, the carrier gas H is turned on₂In the presence of CH₃SiCl₃Introducing H into the bubbling bottle₂Is prepared from CH₃SiCl₃The mixture is carried into a furnace, the pressure and the air flow in the furnace are adjusted, the deposition pressure is 5000Pa, and the deposition time is 4 h; CH (CH)₃SiCl₃The mole ratio of the intermediate C, Si is 1: 2; after the reaction, generating a G-SiCNWs multidimensional hybridization reinforcement on the surface of the PC-SiC;

directly adjusting CH in a CVD furnace without taking out a sample₃SiCl₃-H₂-process parameters of the Ar reaction system, the process parameters comprising: deposition temperature: 1150 degrees; the deposition time is 6 hours; deposition pressure: 5000 Pa; gas flow rate: carrier gas hydrogen gas: 150 mL/min; reaction hydrogen: 4L/min; diluting argon gas: 2L/min; CH (CH)₃SiCl₃: carrying out CVD-SiC coating deposition at 10G/min to obtain a G-SiCNWs toughened CVD-SiC optical coating, namely G-SiCNWs-SiC;

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. An ultra-lightweight C/C-SiC space reflector is characterized in that: the composite material comprises a C/C composite material, a SiC gradient transition layer embedded on the surface of the C/C composite material, and a graphene-SiCNWs multidimensional hybridization enhanced CVD-SiC coating arranged on the surface of the SiC gradient transition layer; the SiC gradient transition layer is abbreviated as PC-SiC, the graphene-SiCNWs multidimensional hybridization enhanced CVD-SiC coating is abbreviated as G-SiCNWs-SiC, the graphene is abbreviated as G, and the SiCNWs are SiC nanowires.

2. An ultra-lightweight C/C-SiC space mirror as claimed in claim 1, wherein: the content of silicon element in the SiC gradient transition layer is gradually increased from the inside of the C/C composite material to the outer surface of the G-SiCNWs-SiC.

3. The method for manufacturing an ultra-lightweight C/C-SiC space mirror according to claim 1 or 2, wherein: the method comprises the following steps:

s2, preparing G-SiCNWs on the surface of PC-SiC in a controllable way:

placing PC-SiC in a reaction zone in a CVD furnace, vacuumizing, and introducing H₂And Ar, when the temperature of the reaction zone reaches the deposition temperature of 1000-Open carrier gas H₂In the presence of CH₃SiCl₃Introducing H into the bubbling bottle₂Is prepared from CH₃SiCl₃The mixture is taken into a furnace, the pressure and the air flow in the furnace are adjusted, the deposition pressure is 2000 and 5000Pa, and the deposition time is 1-4 h; CH (CH)₃SiCl₃The mole ratio of the intermediate C, Si is 1: (1-4); after the reaction, generating a G-SiCNWs multidimensional hybridization reinforcement on the surface of the PC-SiC;

4. The method for preparing an ultra-lightweight C/C-SiC space mirror according to claim 3, wherein the method comprises the following steps: the penetration enhancer comprises Al₂O₃、B₂O₃Or MgO.

5. The method for preparing an ultra-lightweight C/C-SiC space mirror according to claim 3, wherein the method comprises the following steps: in S2, the flow rate is CH₃SiCl₃And H₂In a molar ratio of 1: (1-4).

6. The method for preparing an ultra-lightweight C/C-SiC space mirror according to claim 3, wherein the method comprises the following steps: in S3, the process parameters include: deposition temperature: 1000-1150 degrees; the deposition time is 4-6 hours; deposition pressure: 1000-5000 Pa; gas flow rate: carrier gas hydrogen gas: 50-150 mL/min; reaction hydrogen: 2-4L/min; diluting argon gas: 1-2L/min; CH (CH)₃SiCl₃：5-10g/min。

7. Use of an ultra-lightweight C/C-SiC space mirror according to claim 1 or 2 in a space optical remote sensing system.

8. Use according to claim 7, characterized in that: the space optical remote sensing system comprises a space telescope or a remote sensing investigation camera.