阅读说明：本技术 多层碳化硅/二氧化硅/金刚石复合自支撑膜及制备方法 (Multilayer silicon carbide/silicon dioxide/diamond composite self-supporting film and preparation method thereof ) 是由 马永 于盛旺 郑可 马丹丹 高洁 王永胜 申艳艳 于 2020-06-18 设计创作，主要内容包括：本发明为一种多层碳化硅/二氧化硅/金刚石复合自支撑膜,属于化学气相沉积技术领域。该自支撑膜由SiC/SiO<Sub>2</Sub>梯度复合层与金刚石膜依次交替叠加而成,且顶层和底层均为SiC/SiO<Sub>2</Sub>梯度复合层。制备时,先在石墨表面沉积一层SiC层,然后利用微波氧等离子体刻蚀部分SiC形成SiC/SiO<Sub>2</Sub>梯度复合层,随后在其表面沉积金刚石膜,之后再重复制备SiC层、SiC/SiO<Sub>2</Sub>梯度复合层、沉积金刚石膜的操作过程,最后将石墨基体氧化去除,即可获得多层SiC/SiO<Sub>2</Sub>/金刚石复合的自支撑膜。该复合自支撑膜兼具高硬度,高热导率,高光学透过率以及高温抗氧化能力等诸多优异的性能。(The invention relates to a multilayer silicon carbide/silicon dioxide/diamond composite self-supporting film, belonging to the technical field of chemical vapor deposition. The self-supporting film is made of SiC/SiO 2 The gradient composite layer and the diamond film are alternately overlapped in sequence, and the top layer and the bottom layer are both SiC/SiO 2 And (4) gradient composite layer. During preparation, firstly, a SiC layer is deposited on the surface of graphite, and then partial SiC is etched by utilizing microwave oxygen plasma to form SiC/SiO 2 Gradient composite layer, depositing diamond film on the surface, and repeating the preparation of SiC layer and SiC/SiO 2 Gradient composite layer, operation process of depositing diamond film, and final oxidizing and removing graphite matrix to obtain multilayer SiC/SiO 2 A/diamond composite self-supporting film. The composite self-supporting film has high hardness, high thermal conductivity, and high optical transmittanceAnd high-temperature oxidation resistance and the like.)

1. A multilayer silicon carbide/silicon dioxide/diamond composite self-supporting film is characterized in that: made of SiC/SiO₂The gradient composite layer and the diamond film are alternately overlapped in sequence, and the top layer and the bottom layer are both SiC/SiO₂And (4) gradient composite layer.

2. The multilayer silicon carbide/silica/diamond composite self-supporting film according to claim 1, wherein: SiC/SiO₂The gradient composite layer and the diamond film are prepared by adopting a microwave plasma chemical vapor deposition method.

3. The multilayer silicon carbide/silica/diamond composite self-supporting film according to claim 2, wherein: SiC/SiO₂The thickness of the gradient composite layer is 1-50 μm, and the thickness of the diamond film is 5-200 μm.

4. A method for producing a multilayer silicon carbide/silica/diamond composite self-supporting film according to any one of claims 1 to 3, comprising the steps of:

1) preparing a SiC layer on the surface of a graphite matrix by adopting a microwave plasma chemical vapor deposition method and taking silicon-carbon-containing gas or a mixed gas of the silicon-containing gas and the carbon-containing gas as a precursor and hydrogen as a reaction gas;

2) introducing oxygen, gradually increasing oxygen flow, slowly reducing flow of silicon-carbon-containing gas or mixed gas of silicon-containing gas and carbon-containing gas to 0 value, forming oxygen plasma or oxyhydrogen plasma to perform microwave oxygen plasma etching on the SiC layer, and converting part of SiC into SiO₂To form SiC/SiO₂Gradient composite layer;

3) introducing methane, gradually increasing the flow of methane and gradually reducing the flow of oxygen, and introducing the mixture into the SiC/SiO reactor₂Depositing a diamond film on the gradient composite layer;

4) repeatedly preparing SiC layer and etching to form SiC/SiO₂The operation processes of gradient composite layer and diamond film deposition are repeated and alternated, and finally, a plurality of layers of SiC/SiO with the thickness of 0.1-3mm are formed on the graphite substrate₂A diamond composite layer;

5) inverting the test piece, exposing the graphite substrate in microwave oxygen plasma, oxidizing and removing the graphite substrate to finally obtain complete multilayer SiC/SiO₂A/diamond composite self-supporting film.

5. The method for producing a multilayer silicon carbide/silica/diamond composite self-supporting film according to claim 4, wherein:

the specific preparation method of the SiC layer is as follows: respectively carrying out ultrasonic cleaning and hot air drying on the graphite by using deionized water and absolute ethyl alcohol; placing the cleaned graphite in a microwave plasma chemical vapor deposition experimental device, introducing silicon-carbon-containing gas or mixed gas of silicon-containing gas and carbon-containing gas as a precursor and hydrogen as reaction gas when the furnace is vacuumized to be below 0.1Pa, and preparing a SiC layer on the surface of a graphite substrate; wherein the technological parameters are as follows: the temperature of the graphite substrate is 700-; when the mixed gas of silicon-containing gas and carbon-containing gas is used as a precursor and hydrogen is used as reaction gas, the hydrogen flow is 100-1000sccm, the volume percentage of the carbon-containing gas in the hydrogen is 0.1-10%, and the volume percentage of the silicon-containing gas in the hydrogen is 0.1-10%;

SiC/SiO₂the specific preparation method of the gradient composite layer is as follows: after the deposition of the SiC layer is finished, introducing oxygen, controlling the flow of the silicon-carbon-containing gas or the mixed gas of the silicon-containing gas and the carbon-containing gas to be gradually reduced to 0sccm, gradually increasing the flow of the oxygen to form oxygen plasma or oxyhydrogen plasma in the vacuum chamber, and performing microwave oxygen plasma etching; the parameters of the etching process are as follows: power of 500-kPa, the oxygen flow is 5-1000sccm, the hydrogen flow is 0-500sccm, the substrate temperature is 300-900 ℃, and the etching time is 5 min-5 h;

the specific preparation method of the diamond film comprises the following steps: SiC/SiO₂After the gradient composite layer is prepared, methane is introduced into the device, oxygen introduction is gradually stopped while the flow of the methane is slowly increased, and H is controlled₂The flow rate is 100-₂The volume percentage of the material is 0.5-10%, the gas pressure is 5-20kPa, and the matrix temperature is 850-;

the technological parameters for removing the graphite matrix by oxidation are as follows: the power is 500-.

6. The method for producing a multilayer silicon carbide/silica/diamond composite self-supporting film according to claim 4, wherein: the silicon-carbon containing gas is tetramethylsilane, trichloromethylsilane or tetraethoxysilane.

7. The method for producing a multilayer silicon carbide/silica/diamond composite self-supporting film according to claim 4, wherein: the silicon-containing gas is silicon tetrachloride, trichlorosilane, dichlorosilane, chlorosilane or silane.

8. The method for producing a multilayer silicon carbide/silica/diamond composite self-supporting film according to claim 4, wherein: the carbon-containing gas is a hydrocarbon containing carbon.

Technical Field

The invention relates to the technical field of chemical vapor deposition, in particular to a multilayer silicon carbide/silicon dioxide/diamond composite self-supporting film and a preparation method thereof.

Background

The Chemical Vapor Deposition (CVD) diamond has the excellent performances of high infrared transmittance, low absorption coefficient, good thermal shock resistance, high thermal conductivity and the like, and is an ideal long-wave infrared (8-12 mu m) window and hood material for a high-speed aircraft.

However, the thermal stability of diamond is poor, the surface temperature of a window or a head cover of the aircraft is rapidly increased due to aerodynamic heating in the high-speed flying process of the aircraft, and when the temperature reaches about 650 ℃, the diamond coating begins to be oxidized and converted into graphite in the atmosphere. This problem severely limits their use as infrared windows in high temperature oxidizing environments.

At present, researchers mostly improve the oxidation resistance of the coating by ion implantation or plating double-layer or multi-layer high-temperature-resistant and strong-adhesion coatings. However, on the one hand, some of the oxidation resistant coatings reduce the transmission of diamond, and on the other hand, any coating is not comparable to diamond in terms of heat dissipation, wear resistance, sand erosion resistance, rain erosion resistance, chemical corrosion resistance, etc., and once the oxidation resistant coating fails, the diamond will be oxidized and fail by exposure to oxygen.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provide a multilayer silicon carbide/silicon dioxide/diamond composite self-supporting film. The self-supporting film has high infrared transmittance and excellent high-temperature oxidation resistance, and can reach the use standard of an infrared window.

The invention is realized by the following technical scheme:

multilayer silicon carbide/silicon dioxide/diamondComposite self-supporting film made of SiC/SiO₂The gradient composite layer and the diamond film are alternately overlapped in sequence, and the top layer and the bottom layer are both SiC/SiO₂And (4) gradient composite layer.

As a preferred technical scheme, SiC/SiO₂The gradient composite layer and the diamond film are prepared by adopting a microwave plasma chemical vapor deposition method.

As a preferred technical scheme, SiC/SiO₂The thickness of the gradient composite layer is 1-50 μm, and the thickness of the diamond film is 5-200 μm.

The multilayer SiC/SiO of the invention₂The self-supporting film compounded by diamond is made of SiC/SiO₂The gradient composite layer and the diamond film are formed alternately and repeatedly in sequence, so that the heat dissipation and corrosion resistance of the diamond, namely SiC/SiO₂Oxidation resistance and SiO₂The combination of good permeability is a novel infrared optical window material.

Furthermore, the invention also provides the multilayer SiC/SiO₂The preparation method of the diamond composite self-supporting film specifically comprises the following steps:

1) preparing a SiC layer on the surface of a graphite matrix by adopting a microwave plasma chemical vapor deposition method and taking silicon-carbon-containing gas or a mixed gas of the silicon-containing gas and the carbon-containing gas as a precursor and hydrogen as a reaction gas;

2) introducing oxygen, gradually increasing oxygen flow, slowly reducing flow of silicon-carbon-containing gas or mixed gas of silicon-containing gas and carbon-containing gas to 0 value, forming oxygen plasma or oxyhydrogen plasma to perform microwave oxygen plasma etching on the SiC layer, and converting part of SiC into SiO₂To form SiC/SiO₂Gradient composite layer;

3) introducing methane, gradually increasing the flow of methane while gradually decreasing the flow of oxygen, and introducing the mixture into the reactor at SiC/SiO₂Depositing a diamond film on the gradient composite layer;

4) repeatedly preparing SiC layer and etching to form SiC/SiO₂The operation processes of gradient composite layer and diamond film deposition are repeated and alternated, and finally, a plurality of layers of SiC/SiO with the thickness of 0.1-3mm are formed on the graphite substrate₂A diamond composite layer;

5) inverting the test piece, exposing the graphite substrate in microwave oxygen plasma, oxidizing and removing the graphite substrate to finally obtain complete multilayer SiC/SiO₂A/diamond composite self-supporting film.

As a preferred technical scheme, a specific preparation method of the SiC layer is as follows: respectively carrying out ultrasonic cleaning and hot air drying on the graphite by using deionized water and absolute ethyl alcohol; placing the cleaned graphite in a microwave plasma chemical vapor deposition experimental device, introducing silicon-carbon-containing gas or mixed gas of silicon-containing gas and carbon-containing gas as a precursor and hydrogen as reaction gas when the furnace is vacuumized to be below 0.1Pa, and preparing a SiC layer on the surface of a graphite substrate; wherein the technological parameters are as follows: the temperature of the graphite substrate is 700-; when the mixed gas of silicon-containing gas and carbon-containing gas is used as a precursor and hydrogen is used as reaction gas, the hydrogen flow is 100-1000sccm, the volume percentage of the carbon-containing gas in the hydrogen is 0.1-10%, and the volume percentage of the silicon-containing gas in the hydrogen is 0.1-10%. SiC/SiO₂The specific preparation method of the gradient composite layer is as follows: after the deposition of the SiC layer is finished, introducing oxygen, controlling the flow of the silicon-carbon-containing gas or the mixed gas of the silicon-containing gas and the carbon-containing gas to be gradually reduced to 0sccm, gradually increasing the flow of the oxygen to form oxygen plasma or oxyhydrogen plasma in the vacuum chamber, and performing microwave oxygen plasma etching; the parameters of the etching process are as follows: the power is 500-. The specific preparation method of the diamond film comprises the following steps: SiC/SiO₂After the gradient composite layer is prepared, methane is introduced into the experimental device, oxygen introduction is gradually stopped while the flow of methane is slowly increased, and H is controlled₂The flow rate is 100-₂The volume percentage of the catalyst is 0.5-10%, the gas pressure is 5-20kPa, and the substrate temperature is 850-. The technological parameters for removing the graphite matrix by oxidation are as follows: work (Gong)The rate is 8000W for 500-.

As a preferred technical scheme, the silicon-carbon containing gas is tetramethylsilane (Si (CH)₃)₄TMS), trichloromethylsilane (CH)₃SiCl₃) Or tetraethoxysilane (Si (OC)₂H₅)₄）。

As a preferred technical scheme, the silicon-containing gas is silicon tetrachloride (SiCl)₄) Trichlorosilane (HSiCl)₃) Dichlorosilane (H)₂SiCl₂) Chlorosilane (H3 SiCl) or Silane (SiH)₄）。

Preferably, the carbon-containing gas is a hydrocarbon containing carbon.

The invention relates to a multilayer SiC/SiO₂The self-supporting film is made of SiC and SiO, which have good heat dissipating performance and corrosion resistance₂Has good oxidation resistance, wherein the oxidation resistance of SiC is realized by forming compact SiO₂The protective film is realized by sequentially preparing SiC/SiO₂Gradient composite layer and formation of SiC/SiO by diamond film₂The diamond multilayer composite self-supporting film combines the excellent performances of the two films, wherein the surface layer is designed to be SiC/SiO₂Gradient composite layer, outermost layer of SiC/SiO in use as optical window or head cap₂The SiC in the composite layer is oxidized and converted into SiO₂To form dense SiO₂Film of multilayer SiC/SiO₂The/diamond composite free-standing film provides oxidation protection. In addition, the multilayer film structure also provides multiple layers of protection, the next layer of SiC/SiO once the outermost oxide and diamond films are consumed₂The gradient composite layer is transformed into a new outer oxidation resistant layer, again providing oxidation protection for the multilayer composite self-supporting membrane as a whole.

The invention has the following beneficial effects:

1) the invention adopts the microwave plasma chemical vapor deposition technology to carry out SiC/SiO on the graphite surface for many times₂Preparation of gradient composite layer and growth of diamond filmThe bottom layer and the surface layer are both SiC/SiO₂The gradient composite layer makes the oxygen contact surface of the diamond film completely wrap the oxidation resistant layer in the using process, thereby improving the oxidation resistance of the diamond. By multilayer SiC, SiO₂The diamond film is circularly and alternately compounded, and the high thermal conductivity, high hardness and high corrosion resistance of the diamond and the SiC and SiO can be comprehensively utilized₂Good oxidation resistance and SiO₂Excellent transmittance, so that the obtained multilayer SiC/SiO₂The diamond composite self-supporting film has the advantages of good oxidation resistance, corrosion resistance, excellent heat conduction, good permeability and the like, so that the use standard of an infrared window is completely met.

2) The multilayer SiC/SiO prepared by the invention₂In a/diamond composite self-supporting film, diamond, SiC and SiO₂The three materials have different Coefficients of Thermal Expansion (CTE), wherein CTE_SiC>CTE_Diamond>CTE_SiO2The invention prepares SiC/SiO₂The gradient composite layer ensures that the thermal expansion coefficient of the gradient composite layer is similar to that of diamond, thereby being beneficial to reducing the interface stress generated by the difference of the thermal expansion coefficients and improving the bonding performance between layers; in addition, the multilayer film is also beneficial to reducing the film thickness of each layer of film and reducing the stress of an interlayer interface by increasing the number of layers; the combined effect of these two aspects ensures that the stress in the self-supporting film as a whole is at a low level and does not fail during use due to peeling or cracking of the coating.

3) The invention prepares SiC/SiO₂The diamond multilayer composite film belongs to a self-supporting film and can comprehensively utilize diamond, SiC and SiO₂High permeability of (2), wherein SiO₂The permeability of the composite self-supporting film is superior to that of diamond, the permeability of SiC is lower than that of diamond, and the multilayer composite self-supporting film with different permeabilities can be obtained by controlling the process, so that the application requirements of different occasions are met.

4) Multilayer SiC/SiO of the invention₂During the preparation of the self-supporting film, the flow of oxygen is gradually changed by controlling hydrogen, silicon-carbon-containing gas or mixed gas of silicon-containing gas and carbon-containing gas, and the concentration of reaction gas in the cavity is changed in a step manner, so that the inner layer is formedAnd the components among the layers and the structure also present gradient change distribution in gradual transition, so that the prepared multilayer composite self-supporting film has excellent bonding performance.

5) The chemical vapor deposition diamond generally grows in a columnar crystal mode, and the columnar crystal of the diamond grows continuously along with the increase of the film thickness, so that the breaking strength of the diamond film is reduced continuously₂SiC-SiO in/diamond multilayer composite self-supporting film₂The composite layer is used as an anti-oxidation layer and also becomes a nucleation substrate of each diamond film, the diamond is blocked from continuously growing along the diamond grains on the previous layer, and the re-nucleation and growth of the diamond are promoted, so that the diamond grains are ensured to be finer, and the fracture strength of the diamond and the toughness of the material are enhanced through a fine grain strengthening effect.

6) During the oxidation treatment of the graphite matrix, the oxygen plasma reacts with the graphite to remove the matrix, and then reacts with the lowest SiC layer to convert the matrix into SiC/SiO₂The lowest layer of the gradient composite layer is changed into SiO₂An anti-oxidation layer with more components, and further improves the multilayer SiC/SiO₂The oxidation resistance of the/diamond composite self-supporting film.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments or the prior art descriptions will be briefly introduced, wherein the drawings are used for providing further explanation of the present invention and form a part of the present application, and the exemplary embodiments and the explanation of the present invention are used for explaining the present invention and do not form a limitation to the present invention.

FIG. 1 is a flow chart of the process for preparing the self-supporting film of the present invention.

In the figure: 1- -graphite substrate, 2-SiC layer, 3-SiC/SiO₂Gradient composite layer, 4-diamond film.

Detailed Description

In order that those skilled in the art will better understand the present invention, a more complete and complete description of the present invention is provided below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.