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

Abstract

The invention discloses a diamond-based microwave attenuation material and a preparation method and application thereof. The method comprises the following steps: plating an anti-oxidation film on a CVD diamond growth surface by adopting a radio frequency magnetron sputtering method; the method comprises the following steps: placing a CVD diamond in a vacuum atmosphere furnace, continuously introducing a mixed gas of oxygen and argon, and carrying out multiple heating and cooling circulation oxidation processes in a temperature change range of 780-880 DEG C to realize grain boundary oxidation of a CVD diamond nucleation surface so as to obtain disordered micro grooves gradually expanded and grown from the CVD diamond nucleation surface to a growth surface; the oxidized CVD diamond is soaked in a glucose solution and then transferred into a vacuum atmosphere furnace to be carbonized, an anti-oxidation film is removed through a mechanical grinding method, and the diamond-based microwave body attenuation material is obtained. The diamond-based microwave body attenuation material prepared by the method can effectively solve the problems of poor body distribution of a graphite attenuation phase in a diamond medium phase, poor dielectric property consistency of the diamond-based microwave body attenuation material and the like in a traditional process.

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 and a preparation method and application thereof. Background Art

[0002] As one of the key core components of the traveling wave tube, the attenuator is a microwave absorber made of attenuation material into a specific shape. Its main function is to cut off the input and output feedback paths, absorb the microwave power entering the attenuator, and reduce the reflected waves caused by mismatch, thereby ensuring that the input signal is amplified. After being absorbed by the attenuator, the electromagnetic wave will be converted into heat energy. Therefore, the good thermal conductivity of the attenuation material can ensure that the attenuator works effectively for a long time, thereby ensuring the stable operation of the traveling wave tube.

[0003] With the continuous increase in the frequency and power of traveling wave tubes, the structural size of the attenuator has been reduced to the millimeter or even sub-millimeter level. In order to achieve the purpose of dissipating a large amount of heat energy in a small volume, higher requirements are placed on the thermal conductivity of the attenuation material. However, due to the thermal properties of the BeO and AlN dielectric phase materials themselves, the thermal conductivity of the developed BeO-based and AlN-based attenuation materials is usually lower than 130W / (m·K), which can no longer meet the application requirements of high-frequency and high-power traveling wave tubes.

[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, since the loss tangent of diamond is usually around 10 -5About 1000 nm, it is basically transparent to high-frequency electromagnetic waves. Therefore, it is necessary to introduce an attenuation phase with strong microwave absorption ability into the diamond dielectric phase to prepare diamond-based microwave bulk attenuation materials. Tao Zengliu used 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 high temperature and high pressure sintered diamond-based microwave bulk attenuation materials is limited and difficult to apply on a large scale; Ding Minghui et al. used microwave plasma chemical vapor deposition method 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 still has many questions. In order 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 to achieve the microwave attenuation performance of CVD diamond materials. However, graphite only exists in the surface area ablated by laser, and the volume distribution of graphite attenuation phase in the diamond dielectric phase cannot be achieved, so the attenuation of microwave power is limited and it is not suitable for high-power traveling wave tubes. The applicant has prepared a diamond-graphite composite diamond-based microwave bulk attenuation material using a microwave plasma method, achieving the 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 view of the above problems, it is necessary to provide a new method for preparing a diamond-based microwave body attenuation material with high power microwave absorption capacity and high thermal conductivity and suitable for terahertz traveling wave tubes. Summary of the invention

[0006] Based on the above problems, the first object of the present invention is to provide a method for preparing a diamond-based microwave bulk attenuation material. The preparation method achieves grain boundary oxidation of the CVD diamond nucleation surface by using multiple temperature rise and fall cycles to obtain disorderly grown micro-grooves, thereby allowing the glucose solution to penetrate into the gaps in the micro-grooves and achieve bulk distribution of the graphite attenuation phase in 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 scheme:

[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 mixed gas of oxygen and argon, and performing a temperature rise and fall cycle 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 expand and grow from the CVD diamond nucleation surface to the growth surface;

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

[0014] Since 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 in 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, and by reasonably controlling the temperature rise and fall cyclic oxidation process, the carbon atom etching rate at the grain boundaries of CVD diamond is much higher than the etching rate at the grains, thereby achieving preferential oxidation of carbon atoms at the grain boundaries, so that deeper micro-grooves are formed around the diamond grains. These deeper micro-grooves become spaces for accommodating glucose solutions. After carbonization, a large amount of graphite is loaded on the surface of diamond grains, which not only realizes the volume distribution of graphite attenuation phase in diamond dielectric phase, but also improves the microwave absorption capacity of diamond-based microwave volume attenuation materials. 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 heating and cooling process is 120-300 min, and the temperature change rate is 5-20°C / min, that is, the heating rate is 5-20°C / min, and the cooling rate is 5-20°C / min.

[0017] Further, 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 maximum temperature and the minimum temperature in each heating and cooling cyclic oxidation process is above 40°C, and each heating to the maximum temperature is maintained for 8-10 minutes. It should be noted that if the difference between the maximum temperature and the minimum temperature in the heating and cooling cyclic oxidation process is too large, the grain boundary oxidation will be insufficient. In order to obtain the ideal micro-groove depth, more cycles are required, resulting in a long total oxidation time, which affects the preparation efficiency. However, the increase in the number of cycles will not affect the performance of the final diamond-based microwave body attenuation material; on the contrary, if the difference between the maximum temperature and the minimum temperature in the heating and cooling cyclic oxidation process is too small, for example, less than 40°C, there will be both CVD diamond grain boundary oxidation and excessive oxidation of CVD diamond grains, resulting in the micro-groove depth not being able to reach the required depth, thereby affecting the performance of the final diamond-based microwave body attenuation material.

[0018] Furthermore, in step 2, the oxidation process is carried out for 8-10 times in a temperature range of 780-880°C, and the difference between the highest temperature and the lowest temperature in each temperature 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 point of view, 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 at the same order of magnitude, it can be considered from a macroscopic point of view that the micro-groove structure is evenly distributed around the diamond grain cone structure, which is conducive to the volume distribution of the graphite attenuation phase in the diamond dielectric phase in the final diamond-based microwave volume attenuation material.

[0021] Furthermore, the following pretreatment 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 material of the anti-oxidation film obtained after RF magnetron sputtering is SiO 2 、Al 2O 3 or Y 2 O 3 One or more of the above, with a thickness of 500-800nm.

[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 invention discloses a diamond-based microwave body attenuation material prepared by the preparation method as described above. The diamond-based microwave body attenuation material uses diamond grains as a medium 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 method for preparing a diamond-based microwave body attenuation material. In the method, a temperature rise and fall cyclic oxidation process is used to reasonably control the oxidation of the CVD diamond nucleus 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 realizing the preferential oxidation of the carbon atoms at the grain boundary, so that a deeper micro-groove is formed around the diamond grain, and these micro-grooves become the accommodation space for the 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 grain, which not only realizes the volume distribution of the graphite attenuation phase in the diamond dielectric phase, but also improves the microwave absorption capacity of the diamond-based microwave body attenuation material, effectively solving the problems of the poor volume distribution of the graphite attenuation phase in the diamond dielectric phase and the poor consistency of the dielectric properties of the diamond-based microwave body attenuation material in the traditional process. At the same time, the depth of the micro-groove can be adjusted by controlling the parameters of the temperature rise and fall cyclic oxidation process, thereby controlling the load proportion of the graphite attenuation phase in the diamond-based microwave body attenuation material, so that the attenuation performance of the diamond-based microwave body attenuation material meets the application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The specific implementation modes of the present invention will be further described in detail below in conjunction with 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 property test area distribution diagram of the diamond-based composite attenuation material prepared in Example 2 of the present invention is shown.

[0037] FIG. 5A to FIG. 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. It should be understood by those skilled in the art 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 treated by mechanical grinding, and then placed in a muffle furnace and oxidized at 680°C for 20 min;

[0044] (2) Anti-oxidation film coating: A 700 nm thick Y film is coated on the CVD diamond growth surface by radio frequency magnetron sputtering. 2 O 3 The specific preparation process conditions of the membrane are: room temperature, power 120W, oxygen flow rate 3sccm, argon flow rate 42sccm;

[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 mixed gas of oxygen and argon, with the oxygen flow rate controlled at 27 sccm and the argon flow rate at 73 sccm. When the temperature reached 820°C, the temperature was raised and lowered cyclically, with the temperature change rate set at 10°C / min. After 5 minutes, the temperature reached 870°C, which was kept at that temperature for 10 minutes. The temperature was then lowered to 820°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, with a groove depth of approximately 82% of the thickness of the CVD diamond.

[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 into 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 diamond grains.

[0047] (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. The schematic diagram of its microstructure 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 FIG. 1 shows that the diamond-based microwave attenuation material contains a diamond phase and a graphite phase. The dielectric properties of the microwave attenuation material of 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 FIG. 1 ). 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 treated by mechanical grinding, and then placed in a muffle furnace and oxidized at 630°C for 35 min;

[0051] (2) Anti-oxidation film coating: 580nm thick SiO2 is coated on the CVD diamond growth surface by radio frequency magnetron sputtering. 2The specific preparation process conditions of the membrane are: room temperature, power 100 W, oxygen flow rate 5.5 sccm, 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 mixed gas of oxygen and argon, and the oxygen flow rate is controlled to be 22 sccm and the argon flow rate is 78 sccm. When the temperature reaches 800°C, the temperature is raised and lowered cyclically, and the temperature change rate is set to 8°C / min. After 5 minutes, the temperature 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, and the groove depth is about 88% of the entire CVD diamond thickness;

[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 into the gaps in the micro-grooves. The CVD diamond was then transferred to a vacuum atmosphere furnace and carbonized at a temperature of 520°C and a nitrogen flow rate of 160 sccm to achieve graphite loading on diamond grains.

[0054] (5) Removing 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 properties test device (e.g. Figure 4 Test area selection), the dielectric constant and loss tangent values ​​in the W band are measured as follows FIG. 5A to FIG. 5E As shown, 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, indicating 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 treated by mechanical grinding, and then placed in a muffle furnace and oxidized at 680°C for 20 min;

[0058] (2) Anti-oxidation film coating: A 700 nm thick Y film is coated on the CVD diamond growth surface by radio frequency magnetron sputtering. 2 O 3 The specific preparation process conditions of the membrane are: room temperature, power 120W, oxygen flow rate 3sccm, argon flow rate 42sccm;

[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 mixed gas of oxygen and argon, with the oxygen flow rate controlled at 27 sccm and the argon flow rate at 73 sccm. When the temperature reached 820°C, the temperature was raised and lowered cyclically, with the temperature change rate set at 10°C / min. After 5 minutes, the temperature reached 870°C, which was kept at that 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, with a groove depth of 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 into 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 diamond grains.

[0061] (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. The microscopic schematic 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 property test device. The dielectric constant and loss tangent value 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 weak.

[0063] Comparative Example 2

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

[0065] (2) Anti-oxidation film coating: 580nm thick SiO2 is coated on the CVD diamond growth surface by radio frequency magnetron sputtering. 2 The specific preparation process conditions of the membrane are: room temperature, power 100 W, oxygen flow rate 5.5 sccm, argon flow rate 55 sccm;

[0066] (3) CVD diamond nucleation surface grain boundary oxidation: The CVD diamond coated with an anti-oxidation film was placed in a vacuum atmosphere furnace continuously flowing with a mixed gas of oxygen and argon, with the oxygen flow rate controlled at 22 sccm and the argon flow rate at 78 sccm. The oxidation temperature was maintained at 840°C. After continuous oxidation for 200 min, 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 into the gaps between the diamond grain arrays. The CVD diamond was then transferred to a vacuum atmosphere 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.

[0068] (5) Removing 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 property test device. The dielectric constant and loss tangent value in the W band were measured as follows: Figure 8 As shown in the figure, 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 protection scope 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 plate an 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 mixed gas of oxygen and argon, and performing a temperature rise and fall cycle oxidation process in 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; 3) The oxidized CVD diamond is immersed in a glucose solution, and then transferred to a vacuum atmosphere furnace for carbonization, and the anti-oxidation film is removed by mechanical grinding to obtain a diamond-based microwave attenuation material with diamond grains loaded with graphite.

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 carried out within the 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 pretreatment 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 was set to 100-150W, the oxygen flow rate was 3-10sccm, and the argon flow rate was 40-60sccm; Preferably, 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.

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 carbonization of 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.

Images