Diamond-based microwave attenuation material, preparation method and application thereof

Abstract

The present invention discloses a diamond-based microwave body attenuation material and its preparation method and application. The method comprises: using a radio frequency magnetron sputtering method to plate an anti-oxidation film on the growth surface of a CVD diamond; placing the CVD diamond in a vacuum atmosphere furnace, continuously introducing a mixed gas of oxygen and argon, and using a multiple temperature rise and fall cycle oxidation process within a temperature range of 780-880°C to achieve grain boundary oxidation of the CVD diamond nucleation surface, thereby obtaining disordered micro-grooves that gradually expand and grow from the CVD diamond nucleation surface to the growth surface; immersing the oxidized CVD diamond in a glucose solution, and then transferring it to a vacuum atmosphere furnace for carbonization, and using a mechanical grinding method to remove the anti-oxidation film to obtain a diamond-based microwave body attenuation material. The diamond-based microwave body attenuation material prepared by this method can effectively solve the problems of poor volume distribution of the graphite attenuation phase in the diamond dielectric phase in the traditional process and poor consistency of the dielectric properties of the diamond-based microwave body attenuation material.

Description

Technical Field

[0001] The present invention relates to the field of microwave body attenuation materials, and more specifically to a diamond-based microwave body attenuation material, a preparation method thereof, and applications thereof. Background Art

[0002] As a key component of a traveling wave tube (TWT), the attenuator is a microwave absorber formed from an attenuating material into a specific shape. Its primary function is to cut off the input and output feedback paths, absorbing the microwave power entering the attenuator while reducing reflected waves caused by mismatches, thereby ensuring that the input signal is amplified. After being absorbed by the attenuator, electromagnetic waves are converted into heat energy. Therefore, the excellent thermal conductivity of the attenuating material ensures the attenuator's long-term effective operation, thereby ensuring the stable operation of the TWT.

[0003] As traveling wave tube (TWT) frequencies and powers continue to increase, attenuator dimensions are shrinking to millimeter and even submillimeter scales. This demands higher thermal conductivity from attenuator materials to dissipate large amounts of heat within a compact footprint. However, due to limitations in the inherent thermal properties of BeO and AlN dielectric phases, the thermal conductivity of existing BeO- and AlN-based attenuator materials is typically below 130 W / (m·K), insufficient for high-frequency, high-power TWT applications.

[0004] Diamond has excellent thermal properties, with a thermal conductivity of up to 2000W / (m·K). Diamond also has high mechanical strength and good chemical stability, making it an ideal dielectric phase for microwave attenuation materials. However, due to the loss tangent value of diamond, which is usually around 10 -5It is basically transparent to high-frequency electromagnetic waves. Therefore, it is necessary to introduce an attenuation phase with strong microwave absorption into the diamond dielectric phase to prepare diamond-based microwave bulk attenuation materials. Tao Zengliu used a high-temperature and high-pressure sintering method to achieve the microwave attenuation performance of diamond using diamond micropowder as raw material. However, the size of the high-temperature and high-pressure sintered diamond-based microwave bulk attenuation material is limited, making it difficult to apply on a large scale. Ding Minghui et al. used microwave plasma chemical vapor deposition to prepare boron-doped CVD diamond with microwave attenuation performance. However, since the dielectric properties of boron-doped CVD diamond vary significantly with temperature, its application in high-power terahertz traveling wave tubes remains questionable. To improve the high-temperature stability of the dielectric properties of diamond-based attenuation materials, Ding Minghui et al. used laser ablation to introduce graphite on the surface of CVD diamond, achieving the microwave attenuation performance of CVD diamond materials. However, the graphite only exists in the laser-ablated surface area, and it is impossible to achieve the bulk distribution of the graphite attenuation phase in the diamond dielectric phase. Therefore, the attenuation of microwave power is limited and it is not suitable for high-power traveling wave tubes. The applicant used a microwave plasma method to prepare a diamond-graphite composite diamond-based microwave bulk attenuation material, achieving a bulk distribution of the graphite attenuation phase in the diamond dielectric phase. However, the preparation process easily leads to the deposition of a large amount of non-diamond carbon on the inner wall of the vacuum chamber, which not only reduces the coupling efficiency of the microwave resonant cavity, but also affects the consistency of the dielectric properties of the diamond-based microwave bulk attenuation material.

[0005] In order to solve the above problems, it is necessary to provide a new method for preparing a diamond-based microwave attenuation material with high power microwave absorption capability and high thermal conductivity, which is suitable for use in terahertz traveling wave tubes. Summary of the Invention

[0006] In response to the above problems, the first objective of the present invention is to provide a method for preparing a diamond-based microwave bulk attenuation material. This method utilizes multiple temperature-raising and cooling cycles to oxidize the grain boundaries of the CVD diamond nucleation surface, creating randomly grown microgrooves. This allows glucose solution to penetrate the gaps in the microgrooves, achieving bulk distribution of the graphite attenuation phase within the diamond dielectric phase.

[0007] A second object of the present invention is to provide a diamond-based microwave attenuation material.

[0008] The third object of the present invention is to provide an application of a diamond-based microwave attenuation material in the preparation of an attenuator for a terahertz traveling wave tube.

[0009] In order to achieve the above first object, the present invention adopts the following technical solutions:

[0010] The present invention discloses a method for preparing a diamond-based microwave attenuation material, comprising the following steps:

[0011] 1) Using radio frequency magnetron sputtering method to plate an anti-oxidation film on the growth surface of CVD diamond;

[0012] 2) Placing the CVD diamond coated with an anti-oxidation film in a vacuum atmosphere furnace, continuously introducing a mixture of oxygen and argon, and performing a temperature ramp oxidation process in a temperature range of 780-880°C to achieve grain boundary oxidation of the CVD diamond nucleation surface, thereby obtaining micro-grooves that gradually extend from the CVD diamond nucleation surface to the growth surface;

[0013] 3) Immersing the oxidized CVD diamond in a glucose solution for 3-5 minutes to allow the glucose solution to fully penetrate the gaps in the micro-grooves. The CVD diamond is then transferred to a vacuum furnace for carbonization, and the anti-oxidation film is removed by mechanical grinding to obtain a diamond-based microwave attenuation material with graphite loaded on diamond grains.

[0014] Because there are a large number of grain boundaries in CVD diamond, and the energy of carbon atoms at the grain boundaries is higher than that of carbon atoms within the diamond grains, the oxidation etching rate of CVD diamond at the grain boundaries is higher than that at the grains. Therefore, starting from this point, the applicant aims to further expand the difference in oxidation etching rate between CVD diamond at the grain boundaries and at the grains. By rationally controlling the temperature-up and temperature-down cyclic oxidation process, the carbon atom etching rate at the CVD diamond grain boundaries is much higher than the etching rate at the grains, thereby achieving preferential oxidation of carbon atoms at the grain boundaries, forming deeper micro-grooves around the diamond grains. These deeper micro-grooves become spaces for accommodating glucose solution. After carbonization, a large amount of graphite is loaded on the surface of the diamond grains, which not only achieves the bulk distribution of the graphite attenuation phase in the diamond dielectric phase, but also improves the microwave absorption capacity of the diamond-based microwave bulk attenuation material. If a fixed temperature is maintained for oxidation or the temperature rise and fall cyclic oxidation process is not properly controlled, the grain boundary oxidation and grain oxidation of the CVD diamond may occur simultaneously, resulting in a shallow micro-groove depth, insufficient glucose solution penetration, and affecting the final material properties.

[0015] Furthermore, in the mixed gas of step 2, the argon flow rate is 20-30 sccm, and the oxygen flow rate is 70-80 sccm.

[0016] Furthermore, in step 2, the duration of the temperature increase and decrease process is 120-300 min, and the temperature change rate is 5-20°C / min, that is, the temperature increase rate is 5-20°C / min, and the temperature decrease rate is 5-20°C / min.

[0017] Furthermore, in step 2, multiple temperature ramping cyclic oxidation processes are performed within a temperature range of 780-880°C, and the difference between the maximum and minimum temperatures during each temperature ramping cyclic oxidation process is greater than 40°C. After each temperature ramping to the maximum temperature, the temperature is maintained for 8-10 minutes. It should be noted that if the difference between the maximum and minimum temperatures during the temperature ramping cyclic oxidation process is too large, the grain boundaries will be insufficiently oxidized. In order to obtain the desired micro-groove depth, more cycles will be required, resulting in an excessively long total oxidation time and affecting the preparation efficiency. However, an increase in the number of cycles does not affect the performance of the resulting diamond-based microwave bulk attenuation material. Conversely, if the difference between the maximum and minimum temperatures during the temperature ramping cyclic oxidation process is too small, for example, less than 40°C, CVD diamond grain boundary oxidation and excessive oxidation of CVD diamond grains will occur simultaneously, resulting in the micro-groove depth failing to reach the desired depth, thereby affecting the performance of the resulting diamond-based microwave bulk attenuation material.

[0018] Furthermore, in step 2, the oxidation process is carried out in a temperature range of 780-880°C for 8-10 times, and the difference between the highest temperature and the lowest temperature in each temperature rise and fall cycle is 40-60°C.

[0019] Furthermore, the disordered micro grooves are selected from disordered cone arrays, which can be considered as weed-like groove structures from a macroscopic perspective, and their depth can reach 70-90% of the thickness of the CVD diamond, that is, 70-90% of the distance between the nucleation surface and the growth surface of the CVD diamond.

[0020] It should be noted that since the width of the micro-groove structure formed by the oxidation of the CVD diamond grain boundaries is in the range of several microns and tens of microns, and the diameter of the diamond grain cone structure retained after oxidation is also in the same order of magnitude, it can be considered from a macroscopic perspective that the micro-groove structure is evenly distributed around the diamond grain cone structure, which is conducive to the bulk distribution of the graphite attenuation phase in the diamond dielectric phase in the final diamond-based microwave bulk attenuation material.

[0021] Furthermore, the following pre-treatment steps for CVD diamond are also included before RF magnetron sputtering:

[0022] The mechanically ground CVD diamond was placed in a muffle furnace and pre-oxidized at 550-700°C for 10-40 minutes.

[0023] Furthermore, during the RF magnetron sputtering process, the power is set to 100-150 W, the oxygen flow rate is 3-10 sccm, and the argon flow rate is 40-60 sccm.

[0024] Furthermore, the anti-oxidation film obtained after radio frequency magnetron sputtering is made of one or more of SiO2, Al2O3 or Y2O3, and has a thickness of 500-800 nm.

[0025] Furthermore, the concentration of the glucose solution is 10%-30%; the flow rate of nitrogen introduced during the carbonization process is 100-200 sccm, and the carbonization temperature is 450-550°C.

[0026] In order to achieve the above second purpose, the present invention adopts the following technical solutions:

[0027] The present invention discloses a diamond-based microwave attenuation material prepared by the above-mentioned preparation method. The diamond-based microwave attenuation material uses diamond grains as a dielectric phase and graphite formed by carbonizing glucose as an attenuation phase.

[0028] In order to achieve the third object, the present invention adopts the following technical solutions:

[0029] The present invention discloses an application of the diamond-based microwave attenuation material described above in preparing an attenuator for a terahertz traveling wave tube.

[0030] The beneficial effects of the present invention are as follows:

[0031] The present invention provides a preparation method of a diamond-based microwave bulk attenuation material, in which a temperature-raising and cooling cyclic oxidation process is used to reasonably control the oxidation of the CVD diamond nucleation surface, so that the carbon atom etching rate at the CVD diamond grain boundary is much higher than the etching rate at the grain, thereby achieving preferential oxidation of carbon atoms at the grain boundary, so that deep micro-grooves are formed around the diamond grains. These micro-grooves become a holding space for glucose solution. The glucose solution infiltrated into the micro-grooves is carbonized to load a large amount of graphite on the surface of the diamond grains, not only achieving the volume distribution of the graphite attenuation phase in the diamond dielectric phase, but also improving the microwave absorption capacity of the diamond-based microwave bulk attenuation material, effectively solving the problems of poor volume distribution of the graphite attenuation phase in the diamond dielectric phase and poor consistency of dielectric properties of the diamond-based microwave bulk attenuation material in traditional processes. At the same time, the depth of the micro-grooves can be adjusted by controlling the parameters of the temperature-raising and cooling cyclic oxidation process, thereby controlling the load ratio of the graphite attenuation phase in the diamond-based microwave bulk attenuation material, so that the attenuation performance of the diamond-based microwave bulk attenuation material meets application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] Figure 1 A schematic diagram of the microstructure of the diamond-based microwave attenuation material prepared in Example 1 of the present invention is shown.

[0034] Figure 2 The Raman spectrum of the diamond-based composite attenuation material prepared in Example 1 of the present invention is shown.

[0035] Figure 3 The dielectric properties of the diamond-based composite attenuation material prepared in Example 1 of the present invention are shown.

[0036] Figure 4 The dielectric performance test area distribution diagram of the diamond-based composite attenuation material prepared in Example 2 of the present invention is shown.

[0037] Figures 5A to 5E The dielectric properties of the diamond-based composite attenuation material prepared in Example 2 of the present invention in different test areas are shown, wherein: Figure 5A For area 1, Figure 5B For area 2, Figure 5C For area 3, Figure 5D For area 4, Figure 5E It is area 5.

[0038] Figure 6 A schematic diagram of the microstructure of the diamond-based microwave attenuation material prepared in Comparative Example 1 of the present invention is shown.

[0039] Figure 7 The dielectric properties of the diamond-based composite attenuation material prepared in Comparative Example 1 of the present invention are shown.

[0040] Figure 8 The dielectric properties of the diamond-based composite attenuation material prepared in Comparative Example 2 of the present invention are shown. DETAILED DESCRIPTION

[0041] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0042] Example 1

[0043] (1) CVD diamond pretreatment: The CVD diamond was processed by mechanical grinding, and then placed in a muffle furnace and oxidized at a temperature of 680°C for 20 minutes;

[0044] (2) Anti-oxidation film coating: A 700 nm thick Y2O3 film was deposited on the CVD diamond growth surface using a radio frequency magnetron sputtering method. The specific preparation process conditions were: room temperature, power 120 W, oxygen flow rate 3 sccm, and argon flow rate 42 sccm.

[0045] (3) Oxidation of grain boundaries of CVD diamond nucleation surface: CVD diamond coated with an anti-oxidation film was placed in a vacuum atmosphere furnace continuously flowing with a mixture of oxygen and argon. The oxygen flow rate was controlled to 27 sccm and the argon flow rate was 73 sccm. When the temperature reached 820°C, the temperature was raised and lowered cyclically. The temperature change rate was set to 10°C / min. After 5 minutes, the temperature reached 870°C. The temperature was kept at this temperature for 10 minutes, and then the temperature was lowered to 820°C after 5 minutes. After repeating 8 temperature cycles, i.e., 160 minutes, the preferential oxidation of the CVD diamond grain boundaries was achieved, thereby obtaining disordered micro-grooves that gradually expanded from the CVD diamond nucleation surface to the growth surface. The groove depth was about 82% of the CVD diamond thickness.

[0046] (4) Carbonization with glucose solution: The oxidized CVD diamond was immersed in a 10% glucose solution for 5 min to allow the glucose solution to fully penetrate the gaps in the micro-grooves. The CVD diamond was then transferred to a vacuum furnace and carbonized at 480°C with a nitrogen flow rate of 180 sccm to achieve graphite loading on the diamond grains.

[0047] (5) Removal of the anti-oxidation film layer: The anti-oxidation film on the growth surface is removed by mechanical grinding to obtain a diamond-based microwave attenuation material with diamond grains loaded with graphite. The microstructure diagram is shown in Figure 1 .

[0048] The thermal conductivity of the diamond-based microwave attenuation material at room temperature was measured by a laser thermal conductivity meter to be 179.6 W / (m·K). Figure 2 The Raman spectrum shown in FIG1 shows that the diamond-based microwave bulk attenuation material contains diamond phase and graphite phase. The dielectric properties of the microwave bulk attenuation material with diamond grains loaded with graphite in the W band were measured using a vector network analyzer combined with a material dielectric property testing device. The average dielectric constant in the W band was found to be 6.95, and the average loss tangent was 0.067 (see FIG1 ). Figure 3 ), indicating that the diamond-based microwave attenuation material has good microwave attenuation performance.

[0049] Example 2

[0050] (1) CVD diamond pretreatment: The CVD diamond was processed by mechanical grinding, and then placed in a muffle furnace and oxidized at a temperature of 630°C for 35 minutes;

[0051] (2) Anti-oxidation film coating: A 580 nm thick SiO2 film was deposited on the CVD diamond growth surface using a radio frequency magnetron sputtering method. The specific preparation process conditions were: room temperature, power 100 W, oxygen flow rate 5.5 sccm, and argon flow rate 55 sccm.

[0052] (3) Oxidation of grain boundaries of CVD diamond nucleation surface: CVD diamond coated with an anti-oxidation film is placed in a vacuum atmosphere furnace continuously flowing with a mixture of oxygen and argon. The oxygen flow rate is controlled to 22 sccm and the argon flow rate is 78 sccm. When the temperature reaches 800°C, the temperature is cyclically raised and lowered. The temperature change rate is set to 8°C / min. After 5 minutes, it reaches 840°C and is kept at this temperature for 10 minutes. After another 5 minutes, the temperature is lowered to 800°C. After repeating 10 temperature cycles, i.e., 200 minutes, the preferential oxidation of the CVD diamond grain boundaries is achieved, thereby obtaining disordered micro-grooves that gradually expand and grow from the CVD diamond nucleation surface to the growth surface. The groove depth is about 88% of the thickness of the entire CVD diamond.

[0053] (4) Carbonization with glucose solution: The oxidized CVD diamond was immersed in a 25% glucose solution for 5 min to allow the glucose solution to fully penetrate the gaps in the micro-grooves. The CVD diamond was then transferred to a vacuum furnace and carbonized at a temperature of 520°C and a nitrogen flow rate of 160 sccm to achieve graphite loading on the diamond grains.

[0054] (5) Removal of the anti-oxidation film layer: The anti-oxidation film on the growth surface side is removed by mechanical grinding to obtain a diamond-based microwave attenuation material with diamond grains loaded with graphite.

[0055] The dielectric properties of the edge and center regions of the microwave attenuation material of diamond grain-loaded graphite were measured by a vector network analyzer combined with a material dielectric property testing device (e.g. Figure 4 Test area selection), the dielectric constant and loss tangent values ​​in the W band are measured as follows Figures 5A to 5E As shown in the figure, the average dielectric constants are 8.52 (region 1), 8.21 (region 2), 9.17 (region 3), 10.70 (region 4) and 8.83 (region 5), and the average loss tangents are 0.697 (region 1), 0.638 (region 2), 0.666 (region 3), 0.638 (region 4) and 0.670 (region 5), respectively. This shows that the diamond-based microwave attenuation material has good microwave attenuation performance, and the difference in the average loss tangent in different regions is not large.

[0056] Comparative Example 1

[0057] 1) CVD diamond pretreatment: The CVD diamond was processed by mechanical grinding and then placed in a muffle furnace and oxidized at 680°C for 20 minutes;

[0058] (2) Anti-oxidation film coating: A 700 nm thick Y2O3 film was deposited on the CVD diamond growth surface using a radio frequency magnetron sputtering method. The specific preparation process conditions were: room temperature, power 120 W, oxygen flow rate 3 sccm, and argon flow rate 42 sccm.

[0059] (3) Oxidation of grain boundaries of CVD diamond nucleation surface: CVD diamond coated with an anti-oxidation film was placed in a vacuum atmosphere furnace continuously flowing with a mixture of oxygen and argon. The oxygen flow rate was controlled to 27 sccm and the argon flow rate was 73 sccm. When the temperature reached 820°C, the temperature was raised and lowered cyclically. The temperature change rate was set to 10°C / min. After 5 minutes, the temperature reached 870°C. The temperature was kept at this temperature for 10 minutes. The temperature was then lowered to 855°C after another 5 minutes. After repeating 8 temperature cycles, i.e., 160 minutes, the preferential oxidation of the CVD diamond grain boundaries was achieved, thereby obtaining disordered micro-grooves that gradually expanded from the CVD diamond nucleation surface to the growth surface. The groove depth was about 20% of the CVD diamond thickness.

[0060] (4) Carbonization with glucose solution: The oxidized CVD diamond was immersed in a 10% glucose solution for 5 min to allow the glucose solution to fully penetrate the gaps in the micro-grooves. The CVD diamond was then transferred to a vacuum furnace and carbonized at 480°C with a nitrogen flow rate of 180 sccm to achieve graphite loading on the diamond grains.

[0061] (5) Removal of the anti-oxidation film layer: The anti-oxidation film on the growth surface is removed by mechanical grinding to obtain a diamond-based microwave attenuation material with diamond grains loaded with graphite. The microscopic diagram is shown in Figure 6 .

[0062] The dielectric properties of the diamond-based microwave attenuation material in the W band were measured by a vector network analyzer combined with a material dielectric properties testing device. The dielectric constant and loss tangent values ​​in the W band were measured as follows: Figure 7 As shown, the average dielectric constant in the W band is measured to be 6.19, and the average loss tangent is 0.05. The microwave attenuation ability of the diamond-based microwave body attenuation material is relatively weak.

[0063] Comparative Example 2

[0064] (1) CVD diamond pretreatment: The CVD diamond was processed by mechanical grinding, and then placed in a muffle furnace and oxidized at a temperature of 620°C for 35 minutes;

[0065] (2) Anti-oxidation film coating: A 580 nm thick SiO2 film was deposited on the CVD diamond growth surface using a radio frequency magnetron sputtering method. The specific preparation process conditions were: room temperature, power 100 W, oxygen flow rate 5.5 sccm, and argon flow rate 55 sccm.

[0066] (3) CVD diamond nucleation surface grain boundary oxidation: CVD diamond coated with an anti-oxidation film was placed in a vacuum atmosphere furnace continuously flowing with a mixture of oxygen and argon. The oxygen flow rate was controlled to 22 sccm and the argon flow rate was 78 sccm. The oxidation temperature was maintained at 840°C. After 200 minutes of continuous oxidation, the groove depth was approximately 7% of the entire CVD diamond thickness.

[0067] (4) Carbonization with glucose solution: The oxidized CVD diamond was immersed in a 25% glucose solution for 5 min to allow the glucose solution to fully penetrate the gaps between the diamond grains. The CVD diamond was then transferred to a vacuum furnace and carbonized at 520°C with a nitrogen flow rate of 160 sccm to achieve graphite loading on the diamond grains.

[0068] (5) Removal of the anti-oxidation film layer: The anti-oxidation film on the growth surface side is removed by mechanical grinding to obtain a diamond-based microwave attenuation material with diamond grains loaded with graphite.

[0069] The dielectric properties of the diamond-based microwave attenuation material in the W band were measured by a vector network analyzer combined with a material dielectric properties testing device. The dielectric constant and loss tangent values ​​in the W band were measured as follows: Figure 8 As shown, the average dielectric constant in the W band is 5.38, and the average loss tangent is 8.6×10 -3 The loss tangent of the microwave attenuation material of diamond grain loaded graphite is less than 10 -2 , showing almost no microwave attenuation performance.

[0070] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a diamond-based microwave attenuation material, characterized in that: The steps include: 1) Using radio frequency magnetron sputtering method to deposit anti-oxidation film on the growth surface of CVD diamond; 2) Placing the CVD diamond coated with an anti-oxidation film in a vacuum atmosphere furnace, continuously introducing a mixture of oxygen and argon, and performing a temperature-raising and lowering cycle oxidation process in the temperature range of 780-880°C to achieve grain boundary oxidation of the CVD diamond nucleation surface, thereby obtaining disordered micro-grooves that gradually extend from the CVD diamond nucleation surface to the growth surface; 3) Immersing the oxidized CVD diamond in a glucose solution, then carbonizing it in a vacuum atmosphere furnace, and removing the anti-oxidation film by mechanical grinding to obtain a diamond-based microwave attenuation material with diamond grains loaded with graphite; The material of the anti-oxidation film obtained after radio frequency magnetron sputtering is one or more of SiO2, Al2O3 or Y2O3, and its thickness is 500-800nm.

2. The preparation method according to claim 1, characterized in that In the mixed gas of step 2, the argon flow rate is 20-30 sccm, and the oxygen flow rate is 70-80 sccm.

3. The preparation method according to claim 1, characterized in that In step 2, the temperature rise and fall process lasts for 120-300 minutes, and the temperature change rate is 5-20°C / min.

4. The preparation method according to claim 1, characterized in that In step 2, multiple heating and cooling cyclic oxidation processes are performed within a temperature range of 780-880°C, and the difference between the highest temperature and the lowest temperature in each heating and cooling cyclic oxidation process is above 40°C. After each heating to the highest temperature, the temperature is kept at this temperature for 8-10 minutes.

5. The preparation method according to claim 1, characterized in that The depth of the disordered micro grooves is 70-90% of the thickness of the CVD diamond.

6. The preparation method according to claim 1, characterized in that The following pre-treatment steps are also included for CVD diamond before RF magnetron sputtering: The mechanically ground CVD diamond was placed in a muffle furnace and pre-oxidized at 550-700°C for 10-40 minutes.

7. The preparation method according to claim 1, characterized in that During the RF magnetron sputtering process, the power is set to 100-150 W, the oxygen flow rate is 3-10 sccm, and the argon flow rate is 40-60 sccm.

8. The preparation method according to claim 1, characterized in that The concentration of the glucose solution is 10-30%; the flow rate of nitrogen introduced during the carbonization process is 100-200 sccm, and the carbonization temperature is 450-550°C.

9. The diamond-based microwave attenuation material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The diamond-based microwave body attenuation material uses diamond grains as a medium phase and graphite formed by carbonizing glucose as an attenuation phase.

10. Use of the diamond-based microwave attenuation material according to claim 9 in preparing an attenuator for a terahertz traveling wave tube.

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