A dielectric constant-stable high thermal conductivity diamond-based microwave attenuation material and its preparation method

Abstract

The present application provides a dielectric constant-stable, high-thermal-conductivity diamond-based microwave attenuation material and its preparation method, relating to the technical field of microwave attenuation material preparation. The preparation method comprises: coating an alloy substrate on the surface of a precision-polished graphite substrate, depositing a boron-doped diamond film on the alloy substrate using chemical vapor deposition to obtain a composite sheet; removing the graphite substrate of the composite sheet using slow servo grinding technology, removing the residual graphite substrate and alloy substrate of the composite sheet using a soft metal polishing device, and polishing the deposited surface of the boron-doped diamond film using an automatic grinding device to obtain the high-thermal-conductivity diamond-based microwave attenuation material. This preparation method has the advantages of high microstructural control precision, strong process stability and repeatability, and can achieve efficient preparation of diamond-based microwave attenuation materials.

Description

Technical Field

[0001] The present application relates to the technical field of microwave attenuation material preparation, and in particular to a dielectric constant-stable high thermal conductivity diamond-based microwave attenuation material and a preparation method thereof. Background Art

[0002] Microwave attenuation materials are primarily used to suppress non-designed electromagnetic waves within microwave electronic devices, prevent self-excited oscillations, and improve the terminal electromagnetic matching performance of microwave electronic devices. With the rapid development of modern electronic technology, microwave devices are moving towards miniaturization, high integration, and high-power output. This places higher demands on the dielectric constant stability and thermal conductivity of microwave attenuation materials. Currently, diamond has the highest thermal conductivity among known bulk materials. It can be used in the form of a composite material or made into a film material using chemical vapor deposition. However, untreated diamond films are microwave-transparent materials and cannot be used in the field of microwave attenuation. Boron-doping diamond films can be modified to produce an attenuation effect within the diamond to absorb microwave energy, effectively improving the microwave attenuation performance of diamond films.

[0003] However, commonly used silicon substrate materials, surface polishing techniques, and irrational boron doping can easily reduce the proportion of sp3 hybridized carbon on the surface and within the diamond film, weakening its overall thermal conductivity. Therefore, it is necessary to find a preparation method that can improve the dielectric constant stability while maintaining the overall thermal conductivity of the diamond film and optimize the boron doping process. Summary of the Invention

[0004] Based on this, this application selects graphite material as the substrate, and through a series of technologies such as alloy layer plating, chemical vapor deposition process optimization, step-by-step grinding and polishing of the substrate layer and alloy layer, and micro-damage grinding of the diamond film, a dielectric constant-stable high thermal conductivity diamond-based microwave attenuation material is prepared. This not only ensures the thermal conductivity of the material, but also improves the stability of the dielectric constant, and further expands the application field of diamond-based microwave attenuation materials.

[0005] To achieve the above objectives, the technical solutions of this application are as follows:

[0006] A method for preparing a dielectric constant-stable high thermal conductivity diamond-based microwave attenuation material, comprising:

[0007] An alloy substrate is plated on the surface of a finely polished graphite substrate, and a boron-doped diamond film is deposited on the alloy substrate by chemical vapor deposition to obtain a composite sheet;

[0008] The graphite substrate of the composite sheet is removed by slow servo grinding technology, the residual graphite substrate and alloy substrate of the composite sheet are removed by a soft metal polishing device, and the deposited surface of the boron-doped diamond film is polished by an automatic grinding device to obtain the high thermal conductivity diamond-based microwave attenuation material.

[0009] Preferably, the graphite substrate has a diameter of 34 mm to 38 mm and a thickness of 3.9 mm to 4.5 mm;

[0010] The porosity of the graphite substrate is 0.1%-0.4%;

[0011] The fine polishing treatment comprises: fine polishing the graphite substrate using a magnetic polishing device and polishing powder;

[0012] Preferably, the polishing powder comprises Fe-Cr alloy powder, the mass percentage of Cr is 3.5%-4.2%, and the average particle size of the Fe-Cr alloy powder is 80 μm-96 μm;

[0013] Preferably, the distance between the end of the magnetic brush in the magnetic polishing device and the surface of the graphite substrate is 1.5 mm to 2.1 mm, and the radial rotation speed of the magnetic brush is 270 rpm to 340 rpm;

[0014] Preferably, the time for fine polishing a single side of the graphite substrate is 28s-43s;

[0015] Preferably, the surface roughness Ra value of the substrate after the fine polishing treatment is 0.19 μm-0.42 μm.

[0016] Preferably, the coating of the alloy substrate comprises: evaporating an aluminum-copper alloy using an evaporation plating method to obtain an aluminum-copper alloy substrate;

[0017] Preferably, in the aluminum-copper alloy, the molar ratio of Al to Cu is (2.89-3.23): (0.11-0.18);

[0018] Preferably, when the evaporation coating method is used, the vacuum degree of the evaporation coating chamber is less than 5.6×10 -4 Pa, the current is 122A-132A, the distance between the evaporation source and the graphite substrate is 6cm-11cm, and the rotation speed of the graphite substrate disk is 6rpm-9rpm;

[0019] Preferably, the surface roughness Ra value of the aluminum-copper alloy substrate is 0.11 μm-0.32 μm.

[0020] Preferably, the chemical vapor deposition method comprises: placing the graphite substrate containing the alloy substrate in a vapor deposition device, using CH4 and H2 as precursor gases and amorphous boron as a boron source, performing vapor deposition to obtain the boron-doped diamond film;

[0021] Preferably, the gas volume ratio of CH4 and H2 is (10-14):300;

[0022] Preferably, the boron doping concentration range is 1.1×10 18 -1.3×10 19 cm -3 ;

[0023] Preferably, the core temperature of the vapor deposition device is 860°C-900°C, the power is 5kw-7.5kw, and the pressure is 15kPa-19kPa;

[0024] Preferably, the boron-doped diamond film has a thickness of 0.76 mm to 0.98 mm.

[0025] Preferably, the grinding positive pressure in the slow servo grinding technology is 0.8N-1.3N, and the grinding wheel spindle speed used for grinding is 120rpm-170rpm;

[0026] Preferably, before the slow servo grinding is performed, one side of the boron-doped diamond film of the composite sheet is bonded and fixed to the surface of a fixture;

[0027] Preferably, the grinding is stopped when the thickness of the alloy substrate and the graphite substrate after the slow servo grinding reaches 0.08 mm to 0.11 mm.

[0028] Preferably, when the residual graphite substrate and alloy substrate of the composite sheet are removed by a soft metal polishing device, the soft metal polishing device comprises a metallographic polishing machine;

[0029] Preferably, when using the metallographic polishing machine, the polishing positive pressure of the polishing machine is 0.3N-0.7N, and the spindle speed of the polishing machine is 800rpm-1000rpm;

[0030] Preferably, when using the metallographic polishing machine, the polishing cloth is flannel cloth, and the polishing agent is nano-quartz powder.

[0031] Preferably, the positive grinding pressure of the automatic grinding device is 0.2N-0.4N, the grinding medium is 0.1μm-0.25μm diamond grinding paste, and the grinding disc is tempered flat glass;

[0032] Preferably, the sample disc of the automatic grinding device has a rotation speed of 25 rpm-40 rpm, and the grinding disc has a rotation speed of 60 rpm-70 rpm.

[0033] Preferably, after polishing with an automatic grinding device, the thickness of the high thermal conductivity diamond-based microwave attenuation material obtained is 0.75 mm to 0.97 mm, and the surface roughness Ra value is 0.1 μm to 0.14 μm.

[0034] The present application also provides a dielectric constant-stable high thermal conductivity diamond-based microwave attenuation material, which is prepared using the above-mentioned preparation method.

[0035] Preferably, the thermal conductivity of the high thermal conductivity diamond-based microwave attenuation material is 18.8 W / cm·K-19.6 W / cm·K, and the imaginary part of the relative dielectric constant is 18.5-20.

[0036] Beneficial effects of this application:

[0037] The preparation method of this application uses a graphite substrate, which significantly reduces material costs and ensures good thermal conductivity. The purpose of the substrate surface polishing is to achieve excellent flatness and minimal roughness on the graphite substrate surface, improving the smoothness and flatness of the subsequent diamond film-substrate interface. This eliminates the need for polishing on the side where the diamond film bonds to the substrate, simplifying the process and ensuring surface quality. Plating an alloy substrate on the graphite substrate prevents carbon in the graphite from interfering with the diamond carbon during deposition and facilitates separation of the diamond film from the graphite substrate after deposition without damaging the diamond film. Slow servo grinding technology allows for fine-tuning of the normal pressure based on the amount of grinding, and through real-time monitoring of the thickness to be ground, it prevents excessive substrate wear and effectively protects the diamond film. A soft metal polishing device is used for polishing the alloy substrate, ensuring complete removal of the alloy substrate and further protecting the diamond film surface. An automated grinding device is used to polish the deposited surface of the boron-doped diamond film, preventing the conversion of sp3-hybridized carbon atoms on the diamond film surface to sp2-hybridized carbon atoms, thereby ensuring the thermal conductivity of the boron-doped diamond film. This preparation method has the advantages of high microstructure control precision, process stability and strong repeatability, and can realize the efficient preparation of diamond-based microwave attenuation materials.

[0038] The diamond-based microwave attenuation material of the present application has both a stable dielectric constant and excellent thermal conductivity, thereby expanding the application field of the microwave attenuation material. DETAILED DESCRIPTION

[0039] As used herein:

[0040] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0041] The conjunction "consisting of" excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim, rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0042] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range.

[0043] In these examples, parts and percentages are by mass unless otherwise indicated.

[0044] "Parts by mass" refers to the basic unit of measurement used to express the mass ratio of multiple components. One part can represent any unit of mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, this means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, we could say that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number representing a multiplication factor). It's important to note that, unlike parts by mass, the sum of the mass of all components is not limited to 100 parts.

[0045] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0046] The present application provides a method for preparing a dielectric constant-stable, high-thermal-conductivity diamond-based microwave attenuation material, comprising:

[0047] An alloy substrate is plated on the surface of a finely polished graphite substrate, and a boron-doped diamond film is deposited on the alloy substrate using a chemical vapor deposition method to obtain a composite sheet; the graphite substrate of the composite sheet is removed using a slow servo grinding technology, the residual graphite substrate and alloy substrate of the composite sheet are removed using a soft metal polishing device, and the deposited surface of the boron-doped diamond film is polished using an automatic grinding device to obtain the high thermal conductivity diamond-based microwave attenuation material.

[0048] In an optional embodiment, the substrate material is a high-density graphite substrate with a porosity of 0.1%-0.4%, the diameter of the graphite substrate is 34mm-38mm, for example, it can be 34mm, 35mm, 36mm, 37mm, 38mm or any value between 34mm-38mm, and the thickness is 3.9mm-4.5mm, for example, it can be 3.9mm, 4.0mm, 4.1mm, 4.2mm, 4.3mm, 4.4mm, 4.5mm or any value between 3.9mm-4.5mm.

[0049] When the graphite substrate is finely polished, the method specifically includes: using a magnetic polishing device and polishing powder to finely polish the graphite substrate.

[0050] In an optional embodiment, the polishing powder used for the fine polishing process is Fe-Cr alloy powder with an average particle size of 80 μm-96 μm, wherein the mass percentage of Cr is 3.5%-4.2%.

[0051] In an optional embodiment, the axial angle between the magnetic brush in the magnetic polishing device and the workpiece to be processed is 90°, that is, the axial angle between the magnetic brush and the graphite substrate is 90°.

[0052] The distance between the end of the magnetic brush and the surface of the workpiece to be processed is 1.5mm-2.1mm, that is, the distance between the end of the magnetic brush and the surface of the graphite substrate is 1.5mm-2.1mm, for example, it can be 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.0mm, 2.1mm or any value between 1.5mm-2.1mm.

[0053] The radial rotation speed of the magnetic brush is 270 rpm-340 rpm, for example, it can be 270 rpm, 280 rpm, 290 rpm, 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm or any value between 270 rpm and 340 rpm.

[0054] The single-side fine polishing time of the graphite substrate is 28s-43s, for example, it can be 28s, 30s, 32s, 34s, 36s, 38s, 40s, 43s or any value between 28s and 43s.

[0055] After the above-mentioned fine polishing process, the surface roughness Ra value of the prepared graphite substrate is 0.19μm-0.42μm, for example, it can be 0.19μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.42μm or any value between 0.19μm and 0.42μm.

[0056] In an optional embodiment, an aluminum-copper alloy substrate is obtained by vapor deposition on the fine-polished graphite substrate using an evaporation coating method.

[0057] Specifically, an aluminum-copper alloy is selected as the evaporation source, wherein the molar ratio of Al to Cu in the aluminum-copper alloy is (2.89-3.23):(0.11-0.18), for example, it can be 2.89:0.11, 2.95:0.12, 3:0.15, 3.1:0.18, 3.2:0.16 or any value between (2.89-3.23):(0.11-0.18).

[0058] In a preferred embodiment, when using the evaporation coating method, the vacuum degree of the evaporation coating chamber needs to be less than 5.6×10 -4 Pa, and the instrument current for evaporation deposition is 122A-132A. The distance between the evaporation source in the instrument and the graphite substrate is 6cm-11cm, for example, 6cm, 7cm, 8cm, 9cm, 10cm, 11cm, or any value between 6cm-11cm. The rotation speed of the substrate plate on which the graphite substrate is placed is 6rpm-9rpm, for example, 6rpm, 7rpm, 8rpm, 9rpm, or any value between 6rpm-9rpm.

[0059] After evaporation by the above-mentioned evaporation method, the surface roughness Ra value of the aluminum-copper alloy substrate on the graphite substrate is 0.11μm-0.32μm, for example, it can be 0.11μm, 0.15μm, 0.2μm, 0.24μm, 0.27μm, 0.3μm, 0.32μm or any value between 0.11μm-0.32μm.

[0060] In an optional embodiment, the method for preparing a boron-doped diamond film on an alloy substrate is to use a chemical vapor deposition method, specifically including: placing a graphite substrate containing an alloy substrate in a vapor deposition device, and then using CH4 and H2 as precursor gases and amorphous boron as a boron source to perform chemical vapor deposition to obtain a boron-doped diamond film.

[0061] In a preferred embodiment, the gas volume ratio of the precursor gases CH4 and H2 is (10-14):300, for example, 10:300, 11:300, 12:300, 13:500, 14:100 or any value between (10-14):300.

[0062] After amorphous boron is converted into boron vapor, the boron doping concentration range is 1.1×10 18 -1.3×10 19 cm -3 , for example, it can be 1.1×10 18 cm-3 , 2.5×10 18 cm -3 , 4.3×10 18 cm -3 , 6.5×10 18 cm -3 , 9×10 18 cm -3 , 1×10 19 cm -3 , 1.3×10 19 cm -3 Or 1.1×10 18 ~1.3×10 19 cm -3 Any value in between.

[0063] In an optional embodiment, the core temperature of the vapor deposition device is 860℃-900℃, for example, it can be 860℃, 870℃, 880℃, 890℃, 900μm or any value between 860℃-900℃; the power of the device is 5kw-7.5kw, for example, it can be 5kw, 5.5kw, 6kw, 6.5kw, 7kw, 7.5kw or any value between 5kw-7.5kw; the pressure in the device is 15kPa-19kPa, for example, it can be 15kPa, 16kPa, 17kPa, 18kPa, 19kPa or any value between 15kPa-19kPa.

[0064] After the above chemical vapor deposition process, the thickness of the boron-doped diamond film on the graphite substrate is 0.76mm-0.98mm, for example, it can be 0.76mm, 0.78mm, 0.8mm, 0.82mm, 0.85mm, 0.9mm, 0.95mm, 0.98mm or any value between 0.76mm and 0.98mm.

[0065] After fine polishing and evaporation, an alloy substrate is obtained, and then a boron-doped diamond film is prepared by vapor deposition on the alloy substrate. The final result is a composite sheet consisting of substrate-aluminum-copper alloy substrate-boron-doped diamond film.

[0066] After obtaining the composite sheet, the substrate layer and the alloy substrate layer on the composite sheet need to be removed to obtain a separate boron-doped diamond film, which is the microwave attenuation material.

[0067] In an optional embodiment, slow servo grinding technology is used to remove the graphite substrate from the composite sheet. First, one side of the boron-doped diamond film on the composite sheet is bonded and fixed to the fixture surface. Then, under a positive pressure of 0.8N-1.3N, the graphite substrate is brought into contact with a W20 corundum grinding wheel, and the substrate is ground at a grinding wheel spindle speed of 120rpm-170rpm.

[0068] During the grinding process, an automatic thickness measuring device is used to control the grinding thickness. When the thickness of the alloy substrate and graphite substrate after grinding reaches 0.08mm-0.11mm, the grinding is stopped. At this time, in addition to the boron-doped diamond film, there is still an alloy substrate left on the composite sheet, or there may be some remnants of the graphite substrate.

[0069] Afterwards, a soft metal polishing device is used to remove the alloy substrate and residual graphite substrate of the composite sheet. Specifically, a metallographic polishing machine is used to gradually remove the alloy substrate.

[0070] In a preferred embodiment, when using a metallographic polishing machine, the polishing cloth is selected as flannel cloth, and the polishing agent is selected as nano-quartz powder. The nano-quartz powder has a relatively low hardness and the flannel cloth is relatively tannic, which can ensure that the alloy substrate is completely removed while protecting the surface of the boron-doped diamond film from damage.

[0071] In a preferred embodiment, when using a metallographic polishing machine, the polishing positive pressure of the polishing machine is 0.3N-0.7N, for example, it can be 0.3N, 0.4N, 0.5N, 0.6N, 0.7N or any value between 0.3N-0.7N, and the spindle speed of the polishing machine is 800rpm-1000rpm, for example, it can be 800rpm, 850rpm, 900rpm, 950rpm, 1000rpm or any value between 800rpm-1000rpm.

[0072] After the above process through the metallographic polishing machine, a separate boron-doped diamond film can be obtained. In order to obtain a film layer with better performance, an automatic grinding device is required to polish the deposited surface of the boron-doped diamond film.

[0073] In a preferred embodiment, the automatic grinding device has a normal grinding pressure of 0.2N-0.4N, a grinding medium of 0.1μm-0.25μm diamond paste, a grinding disc of tempered flat glass, a sample disc rotation speed of 25rpm-40rpm, and a grinding disc rotation speed of 60rpm-70rpm. The low grinding rate and low ambient temperature prevent the conversion of sp3 hybridized carbon atoms on the diamond film surface to sp2 hybridized carbon atoms, thereby ensuring the thermal conductivity of the material.

[0074] This application addresses the research and development challenges of commonly used silicon substrate materials, surface polishing techniques, and the irrational doping of boron, which can weaken the thermal conductivity of diamond films. By selecting a highly dense graphite substrate, this application utilizes a series of techniques, including alloy layer coating, chemical vapor deposition process optimization, step-by-step polishing of the substrate and alloy layers, and micro-damage grinding of the diamond film, to prepare a dielectrically stable, high-thermal-conductivity diamond-based microwave attenuation material. The application also investigates the relationship between substrate size, fine polishing process, evaporation coating process, chemical vapor deposition process, substrate grinding process, alloy layer polishing process, and diamond film grinding process, and the microstructure and properties of the diamond-based microwave attenuation material. To obtain a diamond-based microwave attenuation material with a stable dielectric constant and high thermal conductivity, the application screens for the optimal substrate size, fine polishing process, evaporation coating process, chemical vapor deposition process, substrate grinding process, alloy layer polishing process, and diamond film grinding process. The preparation method also boasts advantages such as high microstructural control precision, strong process stability, and repeatability, enabling the efficient preparation of diamond-based microwave attenuation materials.

[0075] After all the above preparation processes, a high thermal conductivity diamond-based microwave attenuation material can be finally prepared. The thickness of the material is 0.75mm-0.97mm, for example, it can be 0.75mm, 0.78mm, 0.8mm, 0.82mm, 0.85mm, 0.9mm, 0.95mm, 0.97mm or any value between 0.75mm-0.97mm.

[0076] After polishing, the surface roughness Ra value of the high thermal conductivity diamond-based microwave attenuation material is 0.1 μm-0.14 μm, for example, it can be 0.1 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm or any value between 0.1 μm and 0.14 μm.

[0077] The high thermal conductivity diamond-based microwave attenuation material prepared by the preparation method has a thermal conductivity of 18.8W / cm·K-19.6W / cm·K, and an imaginary part value of the relative dielectric constant of 18.5-20.

[0078] The embodiments of the present invention will be described in detail below with reference to specific examples, but those skilled in the art will appreciate that the following examples are intended only to illustrate the present invention and should not be construed as limiting the scope of the present invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0079] Example 1

[0080] The method for preparing the diamond-based microwave attenuating material of this embodiment includes:

[0081] (1) First, a high-density graphite substrate with a diameter and thickness of 34 mm and 3.9 mm, respectively, and a porosity of 0.1% was finely polished using a magnetic polishing device. The polishing powder was Fe-3.5% Cr alloy powder with an average particle size of 80 μm. The axial angle between the magnetic brush and the workpiece to be processed was 90°, the distance between the end of the magnetic brush and the workpiece to be processed was 1.5 mm, the radial speed of the magnetic brush was 270 rpm, the single-sided fine polishing time of the substrate was 28 seconds, and the surface roughness Ra value of the substrate after fine polishing was 0.42 μm. Then, the evaporation coating technology was used. An aluminum-copper alloy substrate with a molar ratio of aluminum to copper of 2.89:0.11 was plated on the surface of a precision-polished substrate. The coating thickness was 18 μm, the current was 122 A, the substrate disk speed was 6 rpm, and the evaporation source distance was 6 cm. The surface roughness Ra value of the obtained aluminum-copper alloy substrate was 0.32 μm. The substrate was then placed in an ellipsoidal antenna chemical vapor deposition device to prepare a boron-doped diamond film. The deposition process used CH4 and H2 as precursor gases with a CH4 / H2 volume ratio of 10 / 300. Amorphous boron was used as the boron source, and the boron doping concentration range was 1.1×10 18 cm -3 The core temperature of the deposition device is 860°C, the power is 5 kW, the pressure is 15 kPa, and the thickness of the boron-doped diamond film produced is 0.76 mm.

[0082] (2) The substrate layer of the obtained composite sheet was removed by slow servo grinding technology, with a grinding positive pressure of 0.8 N and a grinding wheel spindle speed of 120 rpm. When the thickness of the alloy substrate and substrate layer reached 0.08 mm, grinding was stopped. The residual substrate and alloy substrate were then removed by a soft metal polishing device, with a polishing positive pressure of 0.3 N and a spindle speed of 800 rpm. Finally, the deposited surface of the boron-doped diamond film was polished by an automatic grinding device, with a grinding positive pressure of 0.2 N and a grinding medium of 0.1 μm diamond grinding paste. The rotation speeds of the sample disk and the grinding disk were 25 rpm and 60 rpm, respectively. Finally, a high thermal conductivity diamond-based microwave attenuation material was obtained.

[0083] Example 2

[0084] (1) First, a high-density graphite substrate with a diameter and thickness of 35 mm and 4.0 mm, respectively, and a porosity of 0.2% was finely polished using a magnetic polishing device. The polishing powder was Fe-3.6% Cr alloy powder with an average particle size of 82 μm. The axial angle between the magnetic brush and the workpiece to be processed was 90°, the distance between the end of the magnetic brush and the surface to be processed was 1.6 mm, the radial speed of the magnetic brush was 280 rpm, the single-sided fine polishing time of the substrate was 29 seconds, and the surface roughness Ra value of the substrate after fine polishing was 0.32 μm. Then, the evaporation coating technology was used. An aluminum-copper alloy substrate with a molar ratio of aluminum to copper of 2.92:0.12 was plated on the surface of a precision-polished substrate. The coating thickness was 19 μm, the current was 123 A, the substrate disk speed was 7 rpm, and the evaporation source distance was 7 cm. The surface roughness Ra value of the obtained aluminum-copper alloy substrate was 0.23 μm. The substrate was then placed in an ellipsoidal antenna chemical vapor deposition device to prepare a boron-doped diamond film. The deposition process used CH4 and H2 as precursor gases with a CH4 / H2 volume ratio of 11 / 300. Amorphous boron was used as the boron source, and the boron doping concentration range was 4.3×10 18 cm -3 The core temperature of the deposition device was 870°C, the power was 5.5 kW, the pressure was 16 kPa, and the thickness of the boron-doped diamond film was 0.78 mm.

[0085] (2) The substrate layer of the obtained composite sheet was removed by slow servo grinding technology, with a grinding positive pressure of 0.9 N and a grinding wheel spindle speed of 130 rpm. When the thickness of the alloy substrate and substrate layer reached 0.09 mm, the grinding was stopped. The residual substrate and alloy substrate were then removed by a soft metal polishing device, with a polishing positive pressure of 0.4 N and a spindle speed of 820 rpm. Finally, the deposited surface of the boron-doped diamond film was polished by an automatic grinding device, with a grinding positive pressure of 0.3 N and a grinding medium of 0.15 μm diamond grinding paste. The rotation speeds of the sample disk and the grinding disk were 30 rpm and 65 rpm, respectively. Finally, a high thermal conductivity diamond-based microwave attenuation material was obtained.

[0086] Example 3

[0087] (1) First, a high-density graphite substrate with a diameter and thickness of 36 mm and 4.2 mm, respectively, and a porosity of 0.3% was finely polished using a magnetic polishing device. The polishing powder was Fe-4.2% Cr alloy powder with an average particle size of 86 μm. The axial angle between the magnetic brush and the workpiece to be processed was 90°, the distance between the end of the magnetic brush and the surface to be processed was 2.1 mm, the radial speed of the magnetic brush was 340 rpm, the single-sided fine polishing time of the substrate was 43 seconds, and the surface roughness Ra value of the substrate after fine polishing was 0.22 μm. Then, the evaporation coating technology was used. An aluminum-copper alloy substrate with a molar ratio of aluminum to copper of 2.95:0.14 was plated on the surface of a precision-polished substrate. The coating thickness was 21 μm, the current was 125 A, the substrate disk speed was 8 rpm, and the evaporation source distance was 8 cm. The surface roughness Ra value of the obtained aluminum-copper alloy substrate was 0.13 μm. The substrate was then placed in an ellipsoidal antenna chemical vapor deposition device to prepare a boron-doped diamond film. The deposition process used CH4 and H2 as precursor gases with a CH4 / H2 volume ratio of 14 / 300. Amorphous boron was used as the boron source, and the boron doping concentration range was 1.3×10 19 cm -3 The core temperature of the deposition device is 900°C, the power is 7kW, the pressure is 17kPa, and the thickness of the boron-doped diamond film produced is 0.85mm;

[0088] (2) The substrate layer of the obtained composite sheet was removed by slow servo grinding technology, with a grinding positive pressure of 0.9 N and a grinding wheel spindle speed of 150 rpm. When the thickness of the alloy substrate and substrate layer reached 0.11 mm, the grinding was stopped. The residual substrate and alloy substrate were then removed by a soft metal polishing device, with a polishing positive pressure of 0.7 N and a spindle speed of 1000 rpm. Finally, the deposited surface of the boron-doped diamond film was polished by an automatic grinding device, with a grinding positive pressure of 0.4 N and a grinding medium of 0.1 μm diamond grinding paste. The rotation speeds of the sample disk and the grinding disk were 30 rpm and 70 rpm, respectively. Finally, a high thermal conductivity diamond-based microwave attenuation material was obtained.

[0089] Example 4

[0090] (1) First, a high-density graphite substrate with a diameter and thickness of 37 mm and 4.3 mm, respectively, and a porosity of 0.4% was finely polished using a magnetic polishing device. The polishing powder was Fe-3.9% Cr alloy powder with an average particle size of 92 μm. The axial angle between the magnetic brush and the workpiece to be processed was 90°, the distance between the end of the magnetic brush and the surface to be processed was 1.8 mm, the radial speed of the magnetic brush was 310 rpm, the single-sided fine polishing time of the substrate was 33 seconds, and the surface roughness Ra value of the substrate after fine polishing was 0.19 μm. Then, the evaporation coating technology was used. An aluminum-copper alloy substrate with a molar ratio of aluminum to copper of 3.23:0.11 was plated on the surface of a precision-polished substrate. The coating thickness was 25 μm, the current was 122 A, the substrate disk speed was 8 rpm, and the evaporation source distance was 10 cm. The surface roughness of the obtained aluminum-copper alloy substrate was Ra0.28 μm. The substrate was then placed in an ellipsoidal antenna chemical vapor deposition device to prepare a boron-doped diamond film. The deposition process used CH4 and H2 as precursor gases with a CH4 / H2 volume ratio of 12 / 300. Amorphous boron was used as the boron source, and the boron doping concentration range was 6.7×10 18 cm -3 The core temperature of the deposition device was 900°C, the power was 7.5 kW, the pressure was 19 kPa, and the thickness of the boron-doped diamond film was 0.98 mm.

[0091] (2) The substrate layer of the obtained composite sheet was removed by slow servo grinding technology, with a grinding positive pressure of 1.3 N and a grinding wheel spindle speed of 120 rpm. When the thickness of the alloy substrate and substrate layer reached 0.08 mm, grinding was stopped. The residual substrate and alloy substrate were then removed by a soft metal polishing device, with a polishing positive pressure of 0.3 N and a spindle speed of 900 rpm. Finally, the deposited surface of the boron-doped diamond film was polished by an automatic grinding device, with a grinding positive pressure of 0.4 N and a grinding medium of 0.1 μm diamond grinding paste. The rotation speeds of the sample disk and the grinding disk were 25 rpm and 70 rpm, respectively. Finally, a high thermal conductivity diamond-based microwave attenuation material was obtained.

[0092] Example 5

[0093] (1) First, a high-density graphite substrate with a diameter and thickness of 37 mm and 3.9 mm, respectively, and a porosity of 0.3% was finely polished using a magnetic polishing device. The polishing powder was Fe-4.2% Cr alloy powder with an average particle size of 87 μm. The axial angle between the magnetic brush and the workpiece to be processed was 90°, the distance between the end of the magnetic brush and the workpiece to be processed was 2.1 mm, the radial speed of the magnetic brush was 300 rpm, the single-sided fine polishing time of the substrate was 38 seconds, and the surface roughness Ra value of the substrate after fine polishing was 0.42 μm. Then, the substrate was subjected to evaporation plating. The technology was used to plate an aluminum-copper alloy substrate with a molar ratio of aluminum to copper of 2.89:0.16 on the surface of a precision-polished substrate. The coating thickness was 21 μm, the current was 128 A, the substrate disk speed was 9 rpm, and the evaporation source distance was 11 cm. The surface roughness of the obtained aluminum-copper alloy substrate was Ra0.18 μm. The substrate was then placed in an ellipsoidal antenna chemical vapor deposition device to prepare a boron-doped diamond film. The deposition process used CH4 and H2 as precursor gases with a CH4 / H2 ratio of 12 / 300, amorphous boron as the boron source, and the boron doping concentration range was 7.8×10 18 cm -3 The core temperature of the deposition device was 860°C, the power was 7.5 kW, the pressure was 19 kPa, and the thickness of the boron-doped diamond film was 0.96 mm.

[0094] 2) Slow servo grinding technology was used to remove the substrate layer of the obtained composite sheet, with a grinding positive pressure of 1.1 N and a grinding wheel spindle speed of 140 rpm. Grinding was stopped when the thickness of the alloy substrate and substrate layer reached 0.08 mm. The remaining substrate and alloy substrate were then removed using a soft metal polishing device, with a polishing positive pressure of 0.3 N and a spindle speed of 850 rpm. Finally, an automatic grinding device was used to polish the deposited surface of the boron-doped diamond film, with a grinding positive pressure of 0.2 N and a grinding medium of 0.15 μm diamond grinding paste. The rotation speeds of the sample disk and the grinding disk were 40 rpm and 60 rpm, respectively, to finally obtain a high thermal conductivity diamond-based microwave attenuation material.

[0095] Example 6

[0096] (1) First, a high-density graphite substrate with a diameter and thickness of 35 mm and 4.3 mm, respectively, and a porosity of 0.4% was finely polished using a magnetic polishing device. The polishing powder was Fe-3.5% Cr alloy powder with an average particle size of 87 μm. The axial angle between the magnetic brush and the workpiece to be processed was 90°, the distance between the end of the magnetic brush and the workpiece to be processed was 1.9 mm, the radial speed of the magnetic brush was 320 rpm, the single-sided fine polishing time of the substrate was 43 seconds, and the surface roughness Ra value of the substrate after fine polishing was 0.19 μm. Then, the substrate was subjected to evaporation plating. The technology was used to plate an aluminum-copper alloy substrate with a molar ratio of aluminum to copper of 3.23:0.18 on the surface of a precision-polished substrate. The coating thickness was 23 μm. The current was 127 A, the substrate disk speed was 8 rpm, and the evaporation source distance was 10 cm. The surface roughness of the obtained aluminum-copper alloy substrate was Ra0.11 μm. The substrate was then placed in an ellipsoidal antenna chemical vapor deposition device to prepare a boron-doped diamond film. The deposition process used CH4 and H2 as precursor gases with a CH4 / H2 ratio of 14 / 300, amorphous boron as the boron source, and the boron doping concentration range was 1.3×10 19 cm -3 The core temperature of the deposition device is 900°C, the power is 6kW, the pressure is 17kPa, and the thickness of the boron-doped diamond film produced is 0.85mm;

[0097] (2) The substrate layer of the obtained composite sheet was removed by slow servo grinding technology, with a grinding positive pressure of 0.8 N and a grinding wheel spindle speed of 140 rpm. When the thickness of the alloy substrate and substrate layer reached 0.09 mm, grinding was stopped. The residual substrate and alloy substrate were then removed by a soft metal polishing device, with a polishing positive pressure of 0.4 N and a spindle speed of 1000 rpm. Finally, the deposited surface of the boron-doped diamond film was polished by an automatic grinding device, with a grinding positive pressure of 0.2 N and a grinding medium of 0.25 μm diamond grinding paste. The rotation speeds of the sample disk and the grinding disk were 40 rpm and 60 rpm, respectively. Finally, a high thermal conductivity diamond-based microwave attenuation material was obtained.

[0098] Example 7

[0099] (1) First, a high-density graphite substrate with a diameter and thickness of 36 mm and 4.5 mm, respectively, and a porosity of 0.4% was finely polished using a magnetic polishing device. The polishing powder was Fe-4.2% Cr alloy powder with an average particle size of 80 to 96 μm. The axial angle between the magnetic brush and the workpiece to be processed was 90°, the distance between the end of the magnetic brush and the surface to be processed was 1.5 mm, the radial speed of the magnetic brush was 270 rpm, the single-sided fine polishing time of the substrate was 28 seconds, and the surface roughness Ra value of the substrate after fine polishing was 0.42 μm. Then, the substrate was steamed and polished. The aluminum-copper alloy substrate with a molar ratio of aluminum to copper of 3.12:0.13 was plated on the surface of a finely polished substrate using the electroplating technology. The coating thickness was 21 μm. The current was 123 A, the substrate disk speed was 7 rpm, and the evaporation source distance was 8 cm. The surface roughness of the obtained aluminum-copper alloy substrate was Ra0.16 μm. The substrate was then placed in an ellipsoidal antenna chemical vapor deposition device to prepare a boron-doped diamond film. The deposition process used CH4 and H2 as precursor gases with a CH4 / H2 ratio of 10 / 300. Amorphous boron was used as the boron source, and the boron doping concentration range was 1.3×10 19 cm -3 The core temperature of the deposition device is 900°C, the power is 5kW, the pressure is 15kPa, and the thickness of the boron-doped diamond film produced is 0.8mm.

[0100] 2) Slow servo grinding technology was used to remove the substrate layer of the obtained composite sheet, with a grinding positive pressure of 1.3 N and a grinding wheel spindle speed of 120 rpm. Grinding was stopped when the thickness of the alloy substrate and substrate layer reached 0.08 mm. The remaining substrate and alloy substrate were then removed using a soft metal polishing device, with a polishing positive pressure of 0.5 N and a spindle speed of 800 rpm. Finally, an automatic grinding device was used to polish the deposited surface of the boron-doped diamond film, with a grinding positive pressure of 0.2 N and a grinding medium of 0.1 μm diamond grinding paste. The rotation speeds of the sample disk and the grinding disk were 30 rpm and 60 rpm, respectively, to finally obtain a high thermal conductivity diamond-based microwave attenuation material.

[0101] Example 8

[0102] (1) First, a high-density graphite substrate with a diameter and thickness of 38 mm and 3.9 mm, respectively, and a porosity of 0.1% was finely polished using a magnetic polishing device. The polishing powder was Fe-4% Cr alloy powder with an average particle size of 82 μm. The axial angle between the magnetic brush and the workpiece to be processed was 90°, the distance between the end of the magnetic brush and the surface to be processed was 1.5 mm, the radial speed of the magnetic brush was 290 rpm, the single-sided fine polishing time of the substrate was 29 seconds, and the surface roughness Ra value of the substrate after fine polishing was 0.35 μm. Then, the substrate was subjected to evaporation coating technology. The surface of a precision-polished substrate was coated with an aluminum-copper alloy substrate with a molar ratio of aluminum to copper of 2.98:0.16. The coating thickness was 24 μm. The current was 130 A, the substrate disk speed was 9 rpm, and the evaporation source distance was 11 cm. The surface roughness of the obtained aluminum-copper alloy substrate was Ra0.32 μm. The substrate was then placed in an ellipsoidal antenna chemical vapor deposition device to prepare a boron-doped diamond film. The deposition process used CH4 and H2 as precursor gases with a CH4 / H2 ratio of 10 / 300. Amorphous boron was used as the boron source, and the boron doping concentration range was 1.1×10 18 cm -3 The core temperature of the deposition device was 860°C, the power was 7.5 kW, the pressure was 19 kPa, and the thickness of the boron-doped diamond film was 0.98 mm.

[0103] 2) Slow servo grinding technology was used to remove the substrate layer of the obtained composite sheet, with a grinding positive pressure of 0.8 N and a grinding wheel spindle speed of 170 rpm. Grinding was stopped when the thickness of the alloy substrate and substrate layer reached 0.11 mm. The remaining substrate and alloy substrate were then removed using a soft metal polishing device, with a polishing positive pressure of 0.7 N and a spindle speed of 1000 rpm. Finally, an automatic grinding device was used to polish the deposited surface of the boron-doped diamond film, with a grinding positive pressure of 0.4 N and a grinding medium of 0.25 μm diamond grinding paste. The rotation speeds of the sample disk and the grinding disk were 25 rpm and 70 rpm, respectively, to finally obtain a high thermal conductivity diamond-based microwave attenuation material.

[0104] The present application tests the performance of the high thermal conductivity diamond-based microwave attenuation materials prepared in Examples 1-4, as shown in Table 1.

[0105] Table 1 Properties of Materials Prepared in Examples 1-4

[0106]

[0107] It can be concluded from the above table that the diamond-based microwave attenuation material prepared in the present application has a stable dielectric constant and excellent thermal conductivity. Its thickness is 0.75-0.97 mm, the surface roughness Ra is 0.10-0.14 μm, the thermal conductivity is 18.8-19.6 W / cm·K, and the imaginary part of the relative dielectric constant is 18.5-20.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0109] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the present invention and to form different embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is intended solely to enhance understanding of the overall background of the present invention and should not be construed as an admission or any form of implication that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a dielectric constant-stable high thermal conductivity diamond-based microwave attenuation material, characterized in that: include: An alloy substrate is plated on the surface of a finely polished graphite substrate, and a boron-doped diamond film is deposited on the alloy substrate by chemical vapor deposition to obtain a composite sheet; The graphite substrate of the composite sheet is removed by slow servo grinding technology, the residual graphite substrate and alloy substrate of the composite sheet are removed by a soft metal polishing device, and the deposited surface of the boron-doped diamond film is polished by an automatic grinding device to obtain the high thermal conductivity diamond-based microwave attenuation material.

2. The preparation method according to claim 1, wherein The graphite substrate has a diameter of 34 mm to 38 mm and a thickness of 3.9 mm to 4.5 mm; The porosity of the graphite substrate is 0.1%-0.4%; The fine polishing treatment includes: using a magnetic polishing device and polishing powder to fine polish the graphite substrate.

3. The preparation method according to claim 2, wherein The polishing powder includes Fe-Cr alloy powder, the mass percentage of Cr is 3.5%-4.2%, and the average particle size of the Fe-Cr alloy powder is 80 μm-96 μm.

4. The preparation method according to claim 2, wherein The distance between the end of the magnetic brush in the magnetic polishing device and the surface of the graphite substrate is 1.5 mm to 2.1 mm, and the radial rotation speed of the magnetic brush is 270 rpm to 340 rpm.

5. The preparation method according to claim 2, wherein The time for fine polishing one side of the graphite substrate is 28s-43s.

6. The preparation method according to claim 2, wherein The surface roughness Ra value of the substrate after the fine polishing treatment is 0.19 μm-0.42 μm.

7. The preparation method according to claim 1, wherein The alloy substrate plating comprises: using an evaporation plating method to evaporate an aluminum-copper alloy to obtain an aluminum-copper alloy substrate.

8. The preparation method according to claim 7, wherein In the aluminum-copper alloy, the molar ratio of Al to Cu is (2.89-3.23): (0.11-0.18).

9. The preparation method according to claim 7, wherein When the evaporation coating method is used, the vacuum degree of the evaporation coating chamber is less than 5.6×10 -4 Pa, the current is 122A-132A, the distance between the evaporation source and the graphite substrate is 6cm-11cm, and the rotation speed of the substrate disk is 6rpm-9rpm.

10. The preparation method according to claim 7, wherein The surface roughness Ra value of the aluminum-copper alloy substrate is 0.11 μm-0.32 μm.

11. The preparation method according to claim 1, wherein The chemical vapor deposition method comprises: placing the graphite substrate containing the alloy substrate in a vapor deposition device, using CH4 and H2 as precursor gases and amorphous boron as a boron source to perform vapor deposition to obtain the boron-doped diamond film.

12. The preparation method according to claim 11, characterized in that The gas volume ratio of CH4 and H2 is (10-14):

300.

13. The preparation method according to claim 11, wherein The boron doping concentration range is 1.1×10 18 -1.3×10 19 cm -3 .

14. The preparation method according to claim 11, wherein The core temperature of the vapor deposition device is 860° C.-900° C., the power is 5 kW-7.5 kW, and the pressure is 15 kPa-19 kPa.

15. The preparation method according to claim 11, wherein The thickness of the boron-doped diamond film is 0.76 mm to 0.98 mm.

16. The preparation method according to claim 1, wherein The grinding positive pressure in the slow servo grinding technology is 0.8N-1.3N, and the grinding wheel spindle speed used for grinding is 120rpm-170rpm.

17. The preparation method according to claim 16, wherein Before the slow servo grinding is performed, one side of the boron-doped diamond film of the composite sheet is bonded and fixed to the surface of a fixture.

18. The preparation method according to claim 16, wherein When the thickness of the alloy substrate and the graphite substrate after the slow servo grinding reaches 0.08 mm to 0.11 mm, the grinding is stopped.

19. The preparation method according to claim 1, wherein When the residual graphite substrate and the alloy substrate of the composite sheet are removed by using a soft metal polishing device, the soft metal polishing device includes a metallographic polishing machine.

20. The preparation method according to claim 19, wherein When the metallographic polishing machine is used, the polishing positive pressure of the polishing machine is 0.3N-0.7N, and the spindle speed of the polishing machine is 800rpm-1000rpm.

21. The preparation method according to claim 20, characterized in that When using the metallographic polishing machine, the polishing cloth is flannel cloth, and the polishing agent is nano-quartz powder.

22. The preparation method according to claim 1, wherein The positive grinding pressure of the automatic grinding device is 0.2N-0.4N, the grinding medium is 0.1μm-0.25μm diamond grinding paste, and the grinding disc is tempered flat glass.

23. The preparation method according to claim 22, characterized in that The sample disc of the automatic grinding device rotates at a speed of 25 rpm to 40 rpm, and the grinding disc rotates at a speed of 60 rpm to 70 rpm.

24. The preparation method according to any one of claims 1 to 23, characterized in that: After polishing with the automatic grinding device, the thickness of the obtained high thermal conductivity diamond-based microwave attenuation material is 0.75 mm to 0.97 mm, and the surface roughness Ra value is 0.1 μm to 0.14 μm.

25. A dielectric constant-stable high thermal conductivity diamond-based microwave attenuation material, characterized in that: It is prepared using the preparation method according to any one of claims 1 to 24.

26. The dielectric constant-stabilized high thermal conductivity diamond-based microwave attenuation material according to claim 25, characterized in that: The thermal conductivity of the high thermal conductivity diamond-based microwave attenuation material is 18.8W / cm·K-19.6W / cm·K, and the imaginary part value of the relative dielectric constant is 18.5-20.

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