Diamond / silicon carbide composite material, apparatus for preparing same, and method for preparing same

Abstract

The present application relates to the technical field of composite materials, and specifically provides a preparation device and method of diamond / silicon carbide composite material and the composite material; the preparation device comprises a furnace body, a heating body, a sintering area, a gas flow meter, a gas inlet, an initial gas pressure control unit, a gas source valve, a gas filling valve, a constant gas pressure control unit, a gas outlet, an evacuation valve, a vacuum pump system, a gas release valve and a constant gas pressure auxiliary unit; the preparation method comprises preparing a diamond preform; and placing the diamond preform and silicon into the preparation device to perform a sintering reaction; by the preparation device, the severe diffusion and reaction of silicon in the infiltration process are controlled by introducing inert protective gas, and the gas flow rate and gas pressure and other parameters in the furnace body are stably regulated and controlled; and the method does not need to add resins, graphite and other carbon sources in the preparation process of the diamond preform, thereby simplifying the process; the prepared composite material reduces the production and preparation cost, and has better thermal and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically providing an apparatus and method for preparing diamond / silicon carbide composite materials, as well as the diamond / silicon carbide composite materials prepared by the apparatus and method. Background Technology

[0002] Diamond / silicon carbide composites have attracted significant attention in numerous industrial applications due to their outstanding properties, including high thermal stability, high specific stiffness, ultra-high hardness, and high wear resistance, particularly in electronic packaging materials, optical components, ceramic armor, and wear-resistant materials. For industrial manufacturing, liquid-phase / gas-phase pressureless reactive infiltration of silicon is a mature technology for preparing high-quality diamond / silicon carbide composites due to its cost-effectiveness and process flexibility.

[0003] The process of preparing diamond / silicon carbide composites by pressureless silicon reactive infiltration is often carried out in a high vacuum state. At this time, silicon, as the main reactant, has a low saturated vapor pressure near the infiltration temperature, which is only about 3~37 Pa at 1550 °C. Therefore, the intense diffusion behavior of silicon during the infiltration process causes the diamond particles to be severely eroded by the reaction. To mitigate the corrosive effect of silicon on diamond, researchers typically incorporate large amounts of resin (pyrolytic carbon obtained through high-temperature degreasing), graphite, and other carbon sources into the diamond preform. These carbon sources then react with silicon in place of diamond during the infiltration process. However, whether using pressureless vapor-phase silicon infiltration (W. Zheng, XB He, M. Wu, et al, Thermal expansion coefficient of Diamond / SiC composites prepared by siliconvapor infiltration in vacuum, Vacuum. 159 (2019) 507-515) or pressureless liquid-phase silicon infiltration (YY Zhang, CY Hsu, P. Karandikar, et al, Interfacial zone surrounding the diamond in reaction bonded diamond / SiC composites: Interphase structure and formation mechanism, J. Eur. Ceram. Soc. 39 (2019) Neither 5190 nor 5196 can effectively guarantee that diamond particles are completely free from the reactive erosion effect of silicon and its graphitization behavior. At the same time, unreacted carbon sources are prone to remain at the interface and transform into graphite inclusions under high temperature, which has an adverse effect on the overall performance and practical application of diamond / silicon carbide composite materials.

[0004] CN 110819313A discloses a method for preparing a diamond / silicon carbide composite material. This method involves repeatedly degreasing, impregnating, and silicon infiltrating a diamond preform to promote the full reaction of silicon with the original carbon source (graphite) and the newly formed carbon source (graphitization of the diamond surface) to produce silicon carbide, thereby obtaining the diamond / silicon carbide composite material. However, this method cannot completely avoid the graphitization of diamond during silicon infiltration, and the complexity and repetitiveness of the process not only reduce production efficiency but also increase preparation costs. Summary of the Invention

[0005] This invention addresses the technical problems existing in existing preparation methods by providing a gas-flow controlled liquid-phase silicon infiltration preparation device and method for high-performance diamond / silicon carbide composite materials. This effectively alleviates the corrosive effect of silicon on diamond particles during the infiltration process. Compared with pressureless infiltration methods, the diamond / silicon carbide composite materials prepared using the device and method of this invention have a reduced degree of diamond graphitization, resulting in higher overall performance.

[0006] This invention provides an apparatus for preparing a diamond / silicon carbide composite material, the apparatus comprising:

[0007] Furnace body, heating element, sintering zone, gas flow meter, air inlet, initial gas pressure control unit, gas source valve, charging valve, constant gas pressure control unit, air outlet, evacuation valve, vacuum pump system, venting valve, and constant gas pressure auxiliary unit;

[0008] The heating element is located at the center of the furnace body, and the sintering zone is located at the center of the heating element; the sintering zone can move up and down along the axial height direction within the heating element.

[0009] The air inlet and the air outlet are located on both sides of the furnace body, respectively.

[0010] The outer side of the air inlet is respectively provided with the air filling valve, the gas flow meter, the initial air pressure control unit, the constant air pressure control unit and the air source valve;

[0011] The air inlet is used to introduce inert protective gas into the furnace body, the gas source valve is used to control the introduction of the inert protective gas, and the gas flow meter is used to monitor the flow rate of the inert protective gas.

[0012] The outer side of the air outlet is respectively provided with the evacuation valve, the vacuum pump system, the vent valve, and the constant pressure auxiliary unit;

[0013] The evacuation valve works in conjunction with the vacuum pump system to create a vacuum environment inside the furnace, and the vent valve is used to control the discharge of inert protective gas from the outlet.

[0014] Preferably, the diameter of the air inlet is smaller than the diameter of the air outlet.

[0015] Preferably, the constant pressure auxiliary unit includes a pressure sensitivity meter, an electronic sensor, and an adjustable pressure counterweight. The constant pressure auxiliary unit is used to correct the pressure parameters set inside the furnace.

[0016] Preferably, the diamond / silicon carbide composite material preparation apparatus further includes an adjustable support mechanism located within the heating body. The adjustable support mechanism supports the sintering zone and allows the sintering zone to move up and down along the axial height direction within the heating body.

[0017] The present invention also provides a method for preparing a diamond / silicon carbide composite material, wherein the method for preparing the diamond / silicon carbide composite material is implemented by the above-described diamond / silicon carbide composite material preparation apparatus.

[0018] Preferably, the preparation method of the diamond / silicon carbide composite material includes the following steps:

[0019] S1: Preparation of diamond preforms;

[0020] S2: The prepared diamond preform and silicon are placed in the preparation device of the diamond / silicon carbide composite material for sintering reaction, and the temperature range of the sintering reaction is 1300 ℃~1650 ℃.

[0021] Preferably, silicon carbide is added during the preparation of the diamond preform.

[0022] Preferably, during the sintering reaction, before the sintering reaction, the vacuum pump system evacuates the furnace at a rate of 800 m³ / s. 3 / s ~2000 m 3 / s; an inert protective gas is introduced into the diamond / silicon carbide composite material preparation device, and the flow rate of the inert protective gas is 1 m / s ~ 5 m / s; by adjusting the constant pressure control unit and the auxiliary unit, the pressure range of the furnace body during the sintering reaction is 50 Pa ~ 500 Pa.

[0023] Preferably, during the sintering reaction, the angle of the inert protective gas through the inlet and outlet is controlled to be horizontal; the height difference between the silicon location and the horizontal height of the inlet is within ±600mm.

[0024] The present invention also provides a diamond / silicon carbide composite material, which is prepared by the above-described method for preparing diamond / silicon carbide composite materials.

[0025] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0026] This invention addresses the problems existing in the preparation of diamond / silicon carbide composite materials using conventional pressureless silicon infiltration methods. It proposes a device and method for preparing diamond / silicon carbide composite materials using airflow-controlled liquid-phase silicon infiltration. Specifically, airflow control effectively mitigates the erosion of diamond by silicon during infiltration, increasing the diamond content in the prepared composite material. Furthermore, no additional carbon source is required during the preparation of the diamond preform, simplifying the process and reducing costs. The method for preparing diamond / silicon carbide composite materials provided by this invention not only overcomes the problems of residual carbon sources in the diamond preform not being completely reacted with silicon and transforming into graphite inclusions, and the easy graphitization of diamond, but also improves the overall performance of the obtained diamond / silicon carbide composite material. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the preparation apparatus for diamond / silicon carbide composite materials according to a specific embodiment of the present invention;

[0028] Figure 2 This is a backscattered electron image of the fracture morphology of the diamond / silicon carbide composite material prepared in Comparative Example 1 according to the present invention.

[0029] Figure 3 yes Figure 2 A magnified image of a local region in the middle;

[0030] Figure 4 This is a backscattered electron image of the fracture morphology of the diamond / silicon carbide composite material prepared in Example 1 of the present invention.

[0031] Figure 5 yes Figure 4 A magnified image of a local region in the middle;

[0032] Figure 6 This is a backscattered electron image of the fracture morphology of the diamond / silicon carbide composite material prepared in Example 2 of the present invention.

[0033] Figure 7 yes Figure 6 A magnified image of a local region in the middle;

[0034] Figure 8 This is a Raman spectrum analysis of the surface of the diamond / silicon carbide composite material inside the diamond particles prepared according to Comparative Example 1 of the present invention.

[0035] Figure 9 This is a Raman spectrum analysis of the surface of the diamond particles inside the diamond / silicon carbide composite material prepared according to Example 1 of the present invention;

[0036] Figure 10This is a Raman spectrum analysis of the surface of the diamond particles inside the diamond / silicon carbide composite material prepared according to Example 2 of the present invention.

[0037] Figure label:

[0038] 1. Furnace body; 2. Heating element; 3. Sintering zone; 4. Gas flow meter; 5. Air inlet; 6. Initial gas pressure control unit; 7. Gas source valve; 8. Gas charging valve; 9. Constant gas pressure control unit; 10. Adjustable support mechanism; 11. Gas outlet; 12. Vacuum valve; 13. Vacuum pump system; 14. Gas release valve; 15. Constant gas pressure auxiliary unit. Detailed Implementation

[0039] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0041] In a specific embodiment of the present invention, an apparatus for preparing diamond / silicon carbide composite materials is provided, such as... Figure 1 The diagram shows a schematic representation of a diamond / silicon carbide composite material preparation apparatus according to a specific embodiment of the present invention. As can be seen from the diagram, the diamond / silicon carbide composite material preparation apparatus includes: 1. a furnace body; 2. a heating element; 3. a sintering zone; 4. a gas flow meter; 5. an air inlet; 6. an initial gas pressure control unit; 7. a gas source valve; 8. a charging valve; 9. a constant gas pressure control unit; 10. an adjustable support mechanism; 11. an air outlet; 12. a vacuum valve; 13. a vacuum pump system; 14. a venting valve; and 15. a constant gas pressure auxiliary unit. The heating element 2 is located at the center of the furnace body 1, and the sintering zone 3 is located at the center of the heating element 2. The sintering zone 3 can move up and down along the axial height direction within the heating element 2. In a specific embodiment, the preparation device further includes an adjustable support mechanism 10, which is located within the heating element 2. The adjustable support mechanism 10 is used to support the sintering zone 3 and allows the sintering zone 3 to move up and down along the axial height direction within the heating element 2, with the movable range not exceeding the heating element 2.

[0042] In specific implementation methods, such as Figure 1As shown, the air inlet 5 and the air outlet 11 are located on both sides of the furnace body 1, respectively. The outer side of the air inlet 5 is provided with the gas filling valve 8, the gas flow meter 4, the initial gas pressure control unit 6, the constant gas pressure control unit 9, and the gas source valve 7. The air inlet 5 is used to introduce inert protective gas into the furnace body 2, the gas source valve 7 is used to control the introduction of the inert protective gas, and the gas flow meter 4 is used to monitor the flow rate of the inert protective gas. The outer side of the air outlet 11 is provided with the vacuum valve 12, the vacuum pump system 13, the vent valve 14, and the constant gas pressure auxiliary unit 15. The vacuum valve 12 works in conjunction with the vacuum pump system 13 to achieve a vacuum environment inside the furnace body 1, and the vent valve 14 is used to control the discharge of the inert protective gas from the air outlet 11.

[0043] In a specific embodiment, the diameter of the air inlet 5 is smaller than the diameter of the air outlet 11. By setting this diameter difference, the power to maintain the vacuum inside the furnace body 1 is greater than the power to cause a significant increase in air pressure due to the introduction of airflow. This ensures that the low air pressure brought by the airflow introduction can be adjusted and optimized for the silicon infiltration process, while also ensuring that there is a certain amount of power during the infiltration process. This better ensures that the preparation device of the present invention can realize the preparation method of liquid phase silicon infiltration based on airflow introduction control under pressureless conditions.

[0044] In a specific implementation, the initial gas pressure control unit 6 is used to control the initial gas pressure inside the furnace body 1, and the constant gas pressure control unit 9 is used to control the gas pressure inside the furnace body 1 to remain constant during the sintering process. The constant gas pressure auxiliary unit 15 may specifically include a pressure sensitivity meter, an electronic sensor, and an adjustable pressure counterweight to correct the gas pressure parameters set inside the furnace body 1. For example, the constant gas pressure control unit 15 controls the gas pressure to 200 Pa. When the actual gas pressure exceeds the required control pressure, the pressure sensitivity meter in the constant gas pressure control unit 15 senses this and uses electronic sensing to control the pressure counterweight to release gas, thereby reducing the gas pressure and achieving the function of constant gas pressure auxiliary control.

[0045] The diamond / silicon carbide composite material preparation apparatus provided in this invention, compared to commonly used vacuum reaction sintering furnaces, ensures that the sintering process is not limited to a vacuum environment. Instead, it introduces airflow to accurately regulate the furnace pressure. This regulation aims to prevent silicon from having an excessively low saturated vapor pressure, which would cause severe evaporation and diffusion, and erode diamond particles in a vacuum environment. Furthermore, by using this apparatus, the gas flow rate and furnace pressure can be accurately and stably controlled during the sintering reaction. This enables the realization of a method for controlling the infiltration of liquid-phase silicon through airflow, resulting in a diamond / silicon carbide composite material with superior performance and properties.

[0046] In a specific embodiment, the present invention also provides a method for preparing a diamond / silicon carbide composite material, wherein the method for preparing the diamond / silicon carbide composite material is implemented by the aforementioned diamond / silicon carbide composite material preparation apparatus.

[0047] Preferably, the preparation method of the diamond / silicon carbide composite material includes the following steps:

[0048] S1: Preparation of diamond preforms;

[0049] In a specific implementation, a diamond preform is first prepared, and then the preform is degreased at high temperature to obtain a diamond preform. Specifically, the diamond preform can be prepared by compression molding, gel casting, or various other methods such as tape casting. In the conventional pressureless (silicon) reactive infiltration process for preparing diamond / silicon carbide composites, a large amount of carbon sources such as graphite and resin are often added to the diamond preform to encapsulate or surround the diamond, in order to replace the diamond being eroded by the silicon reaction. However, this cannot fundamentally solve the problem of diamond being eroded by the silicon reaction. The disadvantage of introducing other carbon sources is that carbon sources that are not completely reacted by silicon are easily transformed into graphite inclusions under high temperature, and thus remain in the composite material, which is detrimental to the structure and performance of the diamond / silicon carbide composite material. However, in the preparation method provided in the specific embodiment of the present invention, the preparation of the diamond preform does not require the addition of other carbon sources such as resin and graphite powder.

[0050] Depending on the actual situation, there are no particular restrictions on the method of obtaining diamond preforms by high-temperature degreasing of the prepared preforms. Specifically, the high-temperature degreasing temperature can be set within 500 ℃ to 2000 ℃. It mainly removes the organic matter introduced during the preparation of the preforms through pyrolysis. Different organic matter is introduced under different methods, so the pyrolysis temperature is also different. It can be set to 500 ℃ to 2000 ℃ or above 500 ℃.

[0051] In a preferred embodiment, silicon carbide is added during the preparation of the diamond preform. Specifically, silicon carbide powder can be added and its particle size distribution and phase content can be controlled with diamond powder according to the actual application. The composite material prepared by the method of this invention mainly consists of diamond and silicon carbide. The final performance of the diamond / silicon carbide composite material is determined by the diamond content, while the silicon is introduced through infiltration to densify the composite material.

[0052] In a specific implementation, taking the preparation of diamond preforms by gel casting as an example, assuming that the maximum diamond content added during the gelation process is 70 vol%, based on this maximum content of 70 vol%, and combined with actual needs, if it is necessary to prepare a composite material with a diamond content of 10 vol%, the preparation method provided by this invention will directly prepare a preform with a diamond content of 10 vol% and a silicon carbide content of 60 vol% during the preparation of the diamond preform; if a diamond content of 20 vol% is required, then the silicon carbide content will be 50 vol%, and so on. The preparation method provided by this invention introduces silicon carbide directly during the preparation of the diamond preform, rather than introducing a carbon source during the preparation of the preform and then allowing the carbon source to react with silicon to generate silicon carbide.

[0053] S2: The prepared diamond preform and silicon are placed in the diamond / silicon carbide composite material preparation device for sintering reaction. The sintering reaction temperature range is 1300 ℃~1650 ℃. In specific embodiments, the added silicon can be in various forms, preferably silicon blocks, and secondly preferably silicon powder. Under vacuum conditions, the evaporation diffusion amount / diffusion flux of silicon blocks is lower than that of silicon powder. Therefore, using silicon blocks is more effective. In the preferred embodiment, the purity of the added silicon is greater than 99.5%, and the resulting composite material has better performance.

[0054] In specific implementations, the ratio of diamond preform to silicon is preferably such that the silicon content just fills the pores of the diamond preform. For example, if a diamond preform with a content of 70 vol% is prepared, the remaining 30 vol% is for pores, and the same amount of silicon is used to fill the pores. Therefore, silicon is added according to the specific content of the diamond preform to ensure that the silicon can fill the preform and achieve densification sintering.

[0055] In a specific embodiment, before the sintering reaction, the vacuum pump system evacuates the furnace at a rate of 800 m³ / s. 3 / s ~2000 m 3 / s; During the sintering reaction, an inert protective gas is introduced into the diamond / silicon carbide composite material preparation device at a flow rate of 1 m / s to 5 m / s; By adjusting the constant pressure control unit and the constant pressure auxiliary unit, the pressure inside the furnace is maintained between 50 Pa and 500 Pa during the sintering reaction; During the sintering reaction, the angle of the inert protective gas through the inlet and outlet is controlled to be horizontal; The height difference between the silicon and the horizontal height of the inlet is within ±600 mm.

[0056] The present invention also provides a diamond / silicon carbide composite material, which is prepared by the above-described method for preparing diamond / silicon carbide composite materials.

[0057] In specific implementation methods, combined with Figure 1 The schematic diagram of the preparation apparatus shown illustrates the following steps in the preparation method of the diamond / silicon carbide composite material provided by this invention:

[0058] (1) First, a diamond preform is prepared using other methods such as gel casting, compression molding, or tape casting. No additional resin, graphite powder, or other carbon sources are required for this step. Silicon carbide powder can be added according to the actual application, and its particle size distribution and phase content can be controlled with the diamond powder. Depending on the specific circumstances, the prepared preform is then subjected to high-temperature degreasing to obtain the diamond preform.

[0059] (2) The prepared diamond preform and silicon are placed in the sintering zone 3 of a vacuum atmosphere sintering furnace with adjustable gas flow rate and pressure; wherein, the inert protective gas can be either argon or helium, and the inert protective gas is introduced through the gas source valve 7 and the gas filling valve 8 at a flow rate of V1 m / s, which is measured by the gas flow meter 4 in the preparation device; the pumping speed of the vacuum pump system 13 is V2 m / s. 3 / s, with an actual pumping speed range of 800~2000 m / s. 3 / s; the diameter of the inlet 5 is D1 mm, and the diameter of the outlet 11 connected to the vacuum pump system 13 is D2 mm. According to the actual furnace body, the following requirements are made: D1 < D2; within the range of 1300℃~1650℃, by adjusting the constant pressure control unit 9 and the constant pressure auxiliary unit 15, the flow rate V1 of the inert protective gas can reach 1 m / s ~ 5 m / s, and the gas pressure in the furnace body 1 can reach 50 Pa ~ 500 Pa; the angles of the inlet 5 and the outlet 11 of the inert protective gas are controlled to be horizontal; and the height difference between the position of silicon in the sintering zone 3 and the horizontal height of the inlet 5 is controlled within ±600 mm.

[0060] (3) Set the temperature program and, according to the requirements set in (2), turn on the vacuum pump system 13 and the pressure control unit system. The pressure control unit system includes an initial pressure control unit 6, a constant pressure control unit 9, and a constant pressure auxiliary unit 15. The specific operation is as follows:

[0061] Step 1: After the furnace body 1 starts to heat up, turn on the vacuum pump system 13. At this time, the furnace body 1 should be kept in a pressureless state.

[0062] Step 2: Before the furnace body 1 is heated to near the melting point of silicon (around 1400 ℃), open the gas source valve 7 and the gas filling valve 8 to introduce argon (or helium). Adjust the initial gas pressure control unit 6, the constant gas pressure control unit 9 and the constant gas pressure auxiliary unit 15 to control the argon flow rate V1 to be constant within the range of m / s1~5 m / s, and control the gas pressure inside the furnace body 1 to be constant within the range of 50Pa~500Pa.

[0063] Step 3: Raise the temperature inside furnace 1 to above the melting point of silicon (the highest temperature is 1650 ℃), and maintain the constant temperature for a period of time. During the constant temperature stage, keep V1 and the gas pressure inside furnace 1 constant.

[0064] Step 4: When the temperature inside furnace 1 drops below the melting point of silicon, stop the argon gas supply and close the gas source valve 7 to keep furnace 1 in a pressureless state; after the entire process is completed, open furnace 1, take out the prepared high-performance diamond / silicon carbide composite material, and perform relevant microstructure characterization, performance testing and application.

[0065] This invention addresses the problems existing in the preparation of diamond / silicon carbide composite materials using conventional pressureless silicon infiltration methods. It proposes a device and method for preparing diamond / silicon carbide composite materials using airflow-controlled liquid-phase silicon infiltration. Specifically, airflow control effectively mitigates the erosion of diamond by silicon during infiltration, increasing the diamond content in the prepared composite material. Furthermore, no additional carbon source is required during the preparation of the diamond preform, simplifying the process and reducing costs. The method for preparing diamond / silicon carbide composite materials provided by this invention not only overcomes the problems of residual carbon sources in the diamond preform not being completely reacted with silicon and transforming into graphite inclusions, and the easy graphitization of diamond, but also improves the overall performance of the obtained diamond / silicon carbide composite material.

[0066] The following detailed description, in conjunction with specific embodiments, provides further details.

[0067] Example 1

[0068] (1) Preparation of diamond preforms

[0069] Diamond / silicon carbide preforms were prepared using an acrylamide gel casting system. The diamond powder particles had sizes of 40 μm and 9 μm, accounting for 50% of the volume, while the silicon carbide powder particles had a size of 40 μm, accounting for 20% of the volume. No other carbon sources such as graphite or resin were added during this preparation process. The prepared diamond preforms were then degreased at 800 °C to obtain the final diamond preform.

[0070] (2) Diamond preform and silicon are placed in a preparation device and sintered.

[0071] The diamond preform prepared in step (1) and a certain mass of silicon block (diamond blank at the bottom and silicon block at the top) are placed in a graphite crucible (the graphite crucible has a boron nitride coating inside and outside), and the crucible is placed in sintering zone 3. The horizontal height difference between the silicon block and the air inlet 5 is 10 mm through the adjustable support mechanism 10.

[0072] (3) Specific operations of airflow-controlled liquid-phase silicon infiltration

[0073] Step 1: After the furnace body 1 starts to heat up, turn on the vacuum pump system 13. At this time, the furnace body 1 can be kept in a pressureless state and the temperature can be raised to 1300 ℃ at a uniform rate.

[0074] Step 2: During the heating stage of furnace body 1 at 1300~1400 ℃, open the gas source valve 7 and the gas filling valve 8 to introduce argon gas, and adjust the initial gas pressure control unit 6, the constant gas pressure control unit 9 and the constant gas pressure auxiliary unit 15 to control V1 to be constant at 1 m / s. At this time, the gas pressure inside furnace body 1 is constant at 120 Pa.

[0075] Step 3: Raise the temperature to 1550 ℃ and maintain it for 30 min. During the constant temperature stage, continue to keep the size of V1 constant at 1 m / s.

[0076] Step 4: When the temperature drops below 1300 ℃, stop the argon gas supply, close the gas source valve 7, keep the furnace body in a pressureless stage, and after the program is completed, open the furnace body to obtain the diamond / silicon carbide composite material.

[0077] Example 2

[0078] The process is basically the same as in Example 1, except that in step (3), the initial pressure control unit 6, the constant pressure control unit 9 and the constant pressure auxiliary unit 15 are adjusted to make the argon flow rate V1 constant at 2 m / s, and the pressure inside the furnace body 1 is constant at 260 Pa; diamond / silicon carbide composite material is prepared.

[0079] Comparative Example 1

[0080] Similar to Example 1, except that in step (3), the inlet 5 is closed, the argon flow rate V1 is 0 m / s, and the furnace pressure is 5 Pa. This example is basically consistent with the conventional method of preparing diamond / silicon carbide composite material by pressureless liquid-phase silicon infiltration, and is used to compare with the diamond / silicon carbide composite material prepared by the methods of Example 1 and Example 2.

[0081] Density, diamond phase content, flexural strength, elastic modulus, and thermal conductivity of the diamond / silicon carbide composite materials prepared in Comparative Example 1, Example 1, and Example 2 were tested respectively. Details are as follows:

[0082] Density: Tested using Archimedes' displacement method;

[0083] Diamond phase content: After polishing, the diamond / silicon carbide composite material was subjected to scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS), and the scanning results were tested using ImageJ (version 1.8.0) software.

[0084] Bending strength and modulus of elasticity: tested using the three-point bending method;

[0085] Thermal conductivity: tested using a laser method;

[0086] The test results are shown in Table 1.

[0087] Table 1

[0088]

[0089] Backscattered electron images (BSD) of the fracture microstructure and morphology of the diamond / silicon carbide composite materials prepared in Comparative Example 1, Example 1, and Example 2 are shown below. Figures 2-7 As shown, specifically, Figure 2 The image shows the fracture morphology of the composite material in Comparative Example 1 at a magnification of 2000x, backscattered electron image. Figure 2 It can be observed that the composite material prepared in Comparative Example 1 has a small number of pores. This is because the diamond surface inside the diamond / silicon carbide composite material prepared by conventional pressureless liquid phase silicon reaction sintering is eroded by silicon reaction to generate silicon carbide, which generates a certain stress, and then the phase peels off during the fracture process. Figure 3 for Figure 2 A magnified image of a local region, magnified 10,000 times, from... Figure 3 As can be seen, in the composite material prepared in Comparative Example 1, there are obvious grooves around the diamond particles caused by the erosion of silicon; while Figure 4 and Figure 6 The images show the fracture morphology backscattered electron images of the composite materials of Examples 1 and 2 at a magnification of 2000. As can be seen from the images, the fracture morphology is complete and dense, without any pores, which fully demonstrates that there is no residual stress inside the diamond / silicon carbide composite materials prepared in Examples 1 and 2. Figure 5 and Figure 7 They are respectively Figure 4 and Figure 6 The magnified images of local areas, magnified 10,000 times, show that the diamond particles inside the composite materials prepared in Examples 1 and 2 have complete morphology and clear boundaries. This fully demonstrates that the diamond / silicon carbide composite material prepared by the method of the present invention effectively mitigates the harmful effects of silicon reaction erosion on diamond.

[0090] In addition, the Raman spectra of the diamond / silicon carbide composite materials prepared in Comparative Example 1, Example 1, and Example 2 are as follows: Figures 8-10 As shown, specifically, from Figure 8 Raman spectroscopy results show that the diamond / silicon carbide composite material prepared by conventional pressureless liquid-phase silicon infiltration in Comparative Example 1 still contains a graphitic phase (due to the exothermic reaction of silicon eroding diamond, local heat rises, leading to graphitization transformation of diamond); from Figure 9 Raman spectroscopy results show that the graphite phase content inside the diamond / silicon carbide composite material prepared by airflow-controlled liquid-phase silicon infiltration in Example 1 of this invention is reduced, i.e., the degree of diamond graphitization is weakened. Similarly, from Figure 10 Raman spectroscopy results also show that the diamond / silicon carbide composite material prepared by airflow-controlled liquid-phase silicon infiltration in Example 2 of this invention does not contain a graphite phase, meaning that the degree of silicon reaction erosion of diamond is effectively mitigated and controlled, and the diamond does not undergo graphitization transformation; at the same time, the Raman peak of pure diamond is 1332 cm⁻¹. -1 When the diamond wave crest shifts to a higher wavenumber, it indicates that it is under compressive stress, specifically from the SiC generated by the surrounding reaction; according to Figures 8-10 The Raman spectroscopy results show that the Raman peak of the diamond in the composite material measured in Comparative Example 1 is 1334 cm⁻¹. -1 This indicates that the silicon reacts and erodes to form silicon carbide, generating a certain compressive stress. The Raman peak of the diamond within the composite material measured in Examples 1 and 2 is 1332 cm⁻¹. -1 This indicates that there is no residual stress inside the prepared composite material; the Raman spectroscopy result also further confirms the presence of residual stress seen in the previous backscattered electron image of the fracture morphology.

[0091] The above performance test results fully demonstrate that the diamond / silicon carbide composite material preparation apparatus provided by the present invention can effectively alleviate the degree of silicon reaction and erosion of diamond during the infiltration process through airflow control, thereby increasing the diamond content in the prepared composite material. At the same time, no additional carbon source needs to be introduced during the preparation of the diamond preform, simplifying the process and reducing the preparation cost. The diamond / silicon carbide composite material preparation method provided by the present invention not only overcomes the problem that the residual carbon source in the diamond preform is not completely reacted by silicon and thus transforms into graphite inclusions and that diamond is prone to graphitization, but also helps to improve the comprehensive performance of the obtained diamond / silicon carbide composite material.

[0092] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0093] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An apparatus for preparing diamond / silicon carbide composite materials, characterized in that, The apparatus for preparing the diamond / silicon carbide composite material includes: Furnace body, heating element, sintering zone, gas flow meter, air inlet, initial gas pressure control unit, gas source valve, charging valve, constant gas pressure control unit, air outlet, evacuation valve, vacuum pump system, venting valve, adjustable support mechanism, and constant gas pressure auxiliary unit; The heating element is located at the center of the furnace body, and the sintering zone is located at the center of the heating element; the sintering zone can move up and down along the axial height direction within the heating element; the adjustable support mechanism is located within the heating element, and the adjustable support mechanism is used to support the sintering zone, so that the sintering zone can move up and down along the axial height direction within the heating element, and the movement range does not exceed the heating element. The air inlet and the air outlet are located on opposite sides of the furnace body; the diameter of the air inlet is smaller than the diameter of the air outlet. The outer side of the air inlet is respectively provided with the air filling valve, the gas flow meter, the initial air pressure control unit, the constant air pressure control unit and the air source valve; The air inlet is used to introduce inert protective gas into the furnace body; the gas source valve is used to control the introduction of the inert protective gas; the gas flow meter is used to monitor the flow rate of the inert protective gas; the initial gas pressure control unit is used to control the initial gas pressure inside the furnace body; and the constant gas pressure control unit is used to control the gas pressure inside the furnace body to remain constant during the sintering process. The outer side of the air outlet is respectively provided with the evacuation valve, the vacuum pump system, the vent valve, and the constant pressure auxiliary unit; The evacuation valve works in conjunction with the vacuum pump system to create a vacuum environment inside the furnace. The venting valve controls the discharge of inert protective gas from the outlet, and the gas pressure is controlled by a constant pressure control unit.

2. The apparatus for preparing diamond / silicon carbide composite material according to claim 1, characterized in that, The constant pressure auxiliary unit includes a pressure sensitivity meter, an electronic sensor, and an adjustable pressure counterweight. The constant pressure auxiliary unit is used to correct the pressure parameters set inside the furnace.

3. A method for preparing a diamond / silicon carbide composite material, characterized in that, The method for preparing the diamond / silicon carbide composite material is implemented using the diamond / silicon carbide composite material preparation apparatus described in any one of claims 1 to 2.

4. The method for preparing the diamond / silicon carbide composite material according to claim 3, characterized in that, The preparation method of the diamond / silicon carbide composite material includes the following steps: S1: Prepare a diamond preform by adding silicon carbide during the preparation of the diamond preform; S2: The prepared diamond preform and silicon are placed in the preparation device of the diamond / silicon carbide composite material for sintering reaction, and the temperature range of the sintering reaction is 1300 ℃~1650 ℃.

5. The method for preparing the diamond / silicon carbide composite material according to claim 4, characterized in that, Silicon carbide is added during the preparation of the diamond preform.

6. The method for preparing the diamond / silicon carbide composite material according to claim 4, characterized in that, Before the sintering reaction, the vacuum pump system is used to evacuate the furnace at a pumping rate of 800 m³ / s. 3 / s ~2000 m 3 / s; During the sintering reaction, an inert protective gas is introduced into the diamond / silicon carbide composite material preparation device, and the flow rate of the inert protective gas is 1 m / s to 5 m / s. By adjusting the constant pressure control unit and the constant pressure auxiliary unit, the pressure inside the furnace during the sintering reaction is made to range from 50 Pa to 500 Pa.

7. The method for preparing the diamond / silicon carbide composite material according to claim 6, characterized in that, During the sintering reaction, the angle of the inert protective gas through the inlet and outlet is controlled to be horizontal; the height difference between the silicon location and the horizontal height of the inlet is within ±600mm.

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