A method for producing a microstructure-based ceramic material and use thereof

Abstract

A preparation method of a ceramic material based on microstructure and application thereof, comprising the following steps: processing a microstructure layer on the surface of a ceramic base, connecting a heat insulation material with the processed ceramic base, and obtaining the ceramic material; wherein the microstructure layer is composed of a plurality of periodically arranged bosses, the bottom surface of the boss is connected with the ceramic base; the bottom surface and the top surface of the boss are concentric squares, the square side length of the top surface is smaller than that of the bottom surface; the cross section shape of the boss is trapezoidal, and the lower base of the trapezoidal shape is connected with the ceramic base. The ceramic material can achieve a wave permeability of more than 70% within 4-18 GHz.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic field and microwave technology, specifically relating to a method for preparing ceramic materials based on microstructures and their applications. Background Technology

[0002] With the development of millimeter-wave technology, the improvement of missile guidance accuracy, and the development of anti-radiation missiles, higher requirements have been placed on the anti-electronic interference capabilities of guidance systems and electronic equipment. This necessitates that their electromagnetic window / cover materials possess excellent broadband characteristics, capable of covering one or more frequency bands. Currently, conventional broadband transparent structural materials include multilayer structures and metamaterial structures.

[0003] However, multilayer structures typically include multiple dielectric layers and frequency-selective surface layers. Since wave-transparent materials have high requirements for total thickness, it is difficult to control the thickness of each layer and the overall thickness when multiple layers exist. Furthermore, the matching problem between layers is also difficult to solve. Most existing metamaterial structures are unit structures of metal or graphite placed on a PI film. These structures are usually two-dimensional, can only accept electromagnetic waves in one or a specific frequency band, and have limited bandwidth extension capabilities, failing to meet the electrical performance requirements for wideband applications (4–18 GHz). Summary of the Invention

[0004] To address the above problems, in a first aspect, this invention proposes a method for preparing microstructure-based ceramic materials, comprising the following steps:

[0005] A microstructure layer is directly processed on the surface of a ceramic substrate; the microstructure layer is made of the same material as the ceramic substrate and is integrally formed.

[0006] The ceramic material is obtained by connecting the thermal insulation material to the processed ceramic matrix.

[0007] The microstructure layer comprises a number of periodically arranged protrusions, the bottom surface of which is connected to the ceramic matrix. The bottom and top surfaces of each protrusion are concentric squares, with the side length of the top square being shorter than that of the bottom square. The cross-sectional shape of each protrusion is trapezoidal, with the lower base of the trapezoid connected to the ceramic matrix. Preferably, the ceramic matrix is ​​a porous silicon nitride ceramic or a quartz fiber-reinforced quartz ceramic matrix composite material, and the microstructure layer is integrally formed with the ceramic matrix.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: the microstructure layer can reduce the number of layers of conventional wave-transmitting materials, which is conducive to simplifying the structure and reducing the matching difficulty between multilayer materials; the microstructure is directly processed on the surface of the ceramic matrix, abandoning the mode of using PI film as a carrier in the traditional method, so that silicon nitride ceramic or quartz fiber reinforced quartz ceramic matrix composite material can be directly used as the medium material of the microstructure, which is conducive to designing the microstructure into a three-dimensional boss structure, which can realize the gradual change of refractive index, expand the bandwidth of the ceramic material, improve the wave transmittance, and enable the wave transmittance of the ceramic material to reach more than 70% in the range of 4 to 18 GHz.

[0009] Preferably, the microstructure layer includes a first structural layer.

[0010] Alternatively, the microstructure layer includes a first structural layer and a second structural layer, wherein the first structural layer and the second structural layer are respectively disposed on two sides of the ceramic substrate;

[0011] The first structural layer is composed of a plurality of first protrusions, and the second structural layer is composed of a plurality of second protrusions.

[0012] The advantages of this preferred solution are as follows: microstructures can be fabricated on both sides of the ceramic substrate, or only on one side of the ceramic substrate; when the ceramic material is actually applied to a product, such as in the manufacture of an radome, if it is fabricated on one side, the first structural layer is located inside the radome; if it is fabricated on both sides, the first structural layer is located inside the radome and the second structural layer is located outside the radome, which helps to improve the transmittance of the ceramic material and its application products. When the microstructure layer includes the first structural layer, the transmittance of the ceramic material can reach more than 70% in the 4–18 GHz range; when the microstructure layer includes both the first and second structural layers, the transmittance of the ceramic material can reach more than 80% in the 4–18 GHz range.

[0013] Preferably, the height H1 of the first boss is 6.3 to 7.3 mm, the side length a1 of the top square is 3.4 to 3.8 mm, the side length b1 of the bottom square is 5.3 to 6.3 mm, and the period P1 is 6.9 to 7.1 mm.

[0014] The height H2 of the second boss is 4.9-5.3 mm, the side length a2 of the top square is 3.1-4.1 mm, the side length b2 of the bottom square is 4.9-5.1 mm, and the period P2 is 6.9-7.1 mm.

[0015] The beneficial effects of this preferred solution are: by limiting the specific height, width, period and other parameters of the first and second protrusions, they can be matched with the thickness, dielectric constant and other parameters of the ceramic substrate, so that the final ceramic material has high wave transmittance and can achieve a wave transmittance of more than 70% in the range of 4 to 18 GHz.

[0016] Preferably, the bottom of the second boss is provided with a chamfer structure between it and the ceramic substrate, and the chamfer structure has an arc-shaped opening with a width of 1 to 1.5 mm.

[0017] The advantages of this preferred solution are: by setting a chamfer structure between the bottom of the second boss and the ceramic substrate, it is beneficial to reduce stress concentration and improve the strength of the ceramic material.

[0018] Preferably, the dielectric constant of the ceramic substrate is 2.9–3.3, the dielectric loss tangent is not greater than 0.008, and the total thickness of the ceramic substrate is 16.1–26.5 mm. More preferably, the total thickness of the ceramic substrate includes the thickness of the microstructure layer, the thickness of which is the height of the first protrusion, or the sum of the heights of the first protrusion and the second protrusion.

[0019] The advantages of this preferred solution are: the ceramic material consists of only two layers, the ceramic matrix and the microstructure layer. Compared with the traditional structure, this effectively reduces the number of layers and allows for more accurate control of the thickness of each layer and the total thickness, thereby improving the wave transmittance.

[0020] Preferably, the material further includes a thermal insulation material connected to the first structural layer. The thermal insulation material has a dielectric constant of 1.1 to 1.4, a dielectric loss tangent of no more than 0.008, and a thickness of 4.8 to 5.2 mm.

[0021] Preferably, the thermal insulation material is connected to the ceramic matrix by an adhesive, wherein the adhesive is aluminum dihydrogen phosphate.

[0022] The advantages of this preferred solution are: by setting up a heat insulation material and limiting the dielectric constant, dielectric loss tangent, and thickness of the heat insulation material, it can be matched with the relevant parameters of the ceramic matrix and microstructure layer. Without affecting the wave transmission performance, the ceramic material can be used for a long time in a high-temperature environment above 1400℃, thus improving reliability.

[0023] Secondly, the present invention proposes a ceramic material prepared based on any of the above-described methods for preparing microstructure-based ceramic materials.

[0024] Compared with existing technologies, the beneficial effects of this invention are as follows: Since the graded refractive index film can broaden both the antireflection wavelength bandwidth and the antireflection angle bandwidth, the subwavelength microstructure layer (i.e., the three-dimensional boss structure) prepared by this invention is theoretically a graded refractive index structure, gradually increasing from the incident medium to the substrate refractive index. When the periodic spacing of the microstructure is sufficiently small, the periodic structure can be considered as many thin sheets, similar to the dielectric layers in a multilayer medium. Each dielectric layer has its equivalent refractive index, which can be calculated using the Braggman equivalent medium approximation theory. Then, the Fresnel formula can be used to calculate the overall reflectivity and transmittance of the microstructure. Therefore, the microstructure layer can achieve a graded refractive index, broaden the bandwidth of the ceramic material, and improve the transmittance, enabling the ceramic material to achieve a transmittance of over 70% within the 4–18 GHz range.

[0025] Thirdly, the present invention proposes the application of a ceramic material prepared by any of the above-described preparation methods in a broadband radome.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: the radome made of the above-mentioned microstructure-based ceramic material can achieve a gradual change in refractive index, receive electromagnetic waves of multiple frequency bands, and make the radome have a transmittance of more than 70% in the range of 4 to 18 GHz. Attached Figure Description

[0027] Figure 1 This is a structural diagram of the ceramic material in an embodiment of the present invention;

[0028] Figure 2 This is a structural diagram of the first structural layer in an embodiment of the present invention;

[0029] Figure 3 This is a structural diagram of the second structural layer in an embodiment of the present invention;

[0030] Figure 4 for Figure 1 Enlarged view of point A in the middle;

[0031] Figure 5 This is a waveform diagram showing the wave transmission performance of the horizontally polarized ceramic material in an embodiment of the present invention.

[0032] Figure 6 This is a waveform diagram showing the wave transmission performance of the ceramic material with vertical polarization in an embodiment of the present invention.

[0033] 1-Ceramic substrate, 2-First structural layer, 2-1-First boss, 3-Second structural layer, 3-1-Second boss, 4-Chamfered structure. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0035] Example 1

[0036] Firstly, such as Figure 1 As shown, this embodiment provides a method for preparing microstructure-based ceramic materials, including the following steps:

[0037] Step 1: Prepare a ceramic matrix 1. The dielectric constant of the ceramic matrix 1 is 2.9–3.3, and the dielectric loss tangent is not greater than 0.008. Optionally, the ceramic matrix 1 can be a porous silicon nitride ceramic or a quartz fiber reinforced quartz ceramic matrix composite. In this embodiment, porous silicon nitride ceramic is preferably used as the ceramic matrix 1. The preparation method of the porous silicon nitride ceramic matrix is ​​as follows:

[0038] Slurry preparation - spray granulation - molding - firing - post-treatment - rough machining - to produce a porous silicon nitride ceramic matrix.

[0039] Step 2: A microstructure layer is fabricated on the surface of a porous silicon nitride ceramic substrate using a custom-made grinding wheel coated with 80# diamond abrasive. The microstructure layer is made of the same material as the ceramic substrate and is integrally formed.

[0040] The microstructure layer consists of several periodically arranged protrusions, the bottom surface of which is connected to the ceramic substrate 1; wherein the bottom and top surfaces of the protrusions are concentric squares, the side length of the square on the top surface is smaller than the side length of the square on the bottom surface; the cross-sectional shape of the protrusion is trapezoidal, and the lower base of the trapezoid is connected to the ceramic substrate.

[0041] The microstructure layer includes a first structural layer 2, or the microstructure layer includes a first structural layer 2 and a second structural layer 3; the first structural layer 2 and the second structural layer 3 are respectively disposed on two sides of the ceramic substrate 1; the thermal insulation material is connected to the first structural layer 2, such as... Figure 1-3As shown, the first structural layer 2 is composed of several first protrusions 2-1, and the second structural layer 3 is composed of several second protrusions 3-1. The height H1 of the first protrusion 2-1 is 6.3–7.3 mm, the side length a1 of the top square is 3.4–3.8 mm, the side length b1 of the bottom square is 5.3–6.3 mm, and the period P1 is 6.9–7.1 mm. The height H2 of the second protrusion 3-1 is 4.9–5.3 mm, the side length a2 of the top square is 3.1–4.1 mm, the side length b2 of the bottom square is 4.9–5.1 mm, and the period P2 is 6.9–7.1 mm. Microstructures can be fabricated on both sides of the ceramic substrate 1, or only on one side of the ceramic substrate 1. When the ceramic material is actually applied to a product, such as in the manufacture of an radome, if it is fabricated on one side, the first structural layer 2 is located inside the radome; if it is fabricated on both sides, the first structural layer 2 is located inside the radome and the second structural layer 3 is located outside the radome, which is beneficial for improving the wave transmittance of the ceramic material and its application products. In this preferred embodiment, the microstructure layer includes a first structural layer 2 and a second structural layer 3, such as... Figure 4 As shown, microstructures are processed on both sides of the ceramic substrate 1. A chamfer structure 4 is provided between the bottom of the second protrusion 3-1 and the ceramic substrate 1. The chamfer structure 4 has an arc-shaped opening with a width of 1 to 1.5 mm.

[0042] In this preferred embodiment, the total thickness of the ceramic substrate 1 is 26.1 to 26.5 mm. The total thickness of the ceramic substrate 1 includes the thickness of the microstructure layer. The thickness of the microstructure layer is the height of the first protrusion 2-1, or the sum of the heights of the first protrusion 2-1 and the second protrusion 3-1. In this embodiment, the total thickness of the ceramic substrate 1 includes the height of the first protrusion 2-1 and the height of the second protrusion 3-1.

[0043] Step 3: Prepare the heat insulation material according to the preparation process of slurry preparation-molding-firing-processing; as an optional solution, the heat insulation material can be heat insulation tile or aerogel composite material. In this embodiment, heat insulation tile is preferred. The dielectric constant of the heat insulation tile is 1.1 to 1.4, the dielectric loss tangent is not greater than 0.008, and the thickness is 4.8 to 5.2 mm.

[0044] Step 4: The thermal insulation material is connected to the first structural layer 2 using a high-temperature resistant inorganic adhesive to obtain the ceramic material. Preferably, in this embodiment, the adhesive is aluminum dihydrogen phosphate.

[0045] Secondly, this embodiment also provides a ceramic material prepared based on any of the above-described methods for preparing microstructure-based ceramic materials. For example... Figure 5 , 6As shown, the ceramic material can achieve a gradual change in refractive index and receive electromagnetic waves in multiple frequency bands, so that the transmittance of the ceramic material can reach more than 80% in the range of 4 to 18 GHz.

[0046] Thirdly, this embodiment also provides an application of ceramic materials prepared by any of the above-described preparation methods in broadband radomes.

[0047] Example 2

[0048] The difference between this embodiment and Embodiment 1 is that:

[0049] (1) The ceramic matrix 1 is a quartz fiber reinforced quartz ceramic matrix composite material, and the preparation method of the quartz fiber reinforced quartz ceramic matrix composite material is as follows:

[0050] Quartz fiber preforms are prepared, and the preforms are repeatedly impregnated and dried and then rough processed to obtain a green body. The green body is then repeatedly impregnated and dried and heat-treated to obtain a quartz fiber reinforced quartz ceramic matrix composite material.

[0051] (2) The microstructure layer includes a first structural layer 2, or the microstructure layer includes a first structural layer 2 and a second structural layer 3; preferably in this embodiment, the microstructure layer only includes the first structural layer 2, which is located inside the radome during fabrication. The total thickness of the ceramic substrate 1 is 16.1–20.5 mm, and the total thickness of the ceramic substrate 1 includes the height of the first boss 2-1.

[0052] (3) The thermal insulation material described in this embodiment is an aerogel composite material with a dielectric constant of 1.1 to 1.4, a dielectric loss tangent of no more than 0.008, and a thickness of 4.8 to 5.2 mm.

[0053] (4) The ceramic material prepared by the preparation method of this embodiment can achieve a gradual change in refractive index, receive electromagnetic waves in multiple frequency bands, and achieve a transmittance of more than 70% in the range of 4 to 18 GHz.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing ceramic materials based on microstructure, characterized in that, Includes the following steps: A microstructure layer is machined on the surface of a porous silicon nitride ceramic substrate using a custom-made grinding wheel coated with 80# diamond abrasive. The microstructure layer is integrally formed with the ceramic substrate. The ceramic material is obtained by connecting the thermal insulation material to the processed ceramic matrix. The microstructure layer is composed of several periodically arranged protrusions, the bottom surface of which is connected to the ceramic substrate; the bottom and top surfaces of the protrusions are concentric squares, with the side length of the top square being shorter than the side length of the bottom square; the cross-sectional shape of the protrusions is trapezoidal, and the lower base of the trapezoid is connected to the ceramic substrate. The microstructure layer includes a first structural layer, or the microstructure layer includes a first structural layer and a second structural layer, wherein the first structural layer and the second structural layer are respectively disposed on two sides of the ceramic substrate; The first structural layer is composed of a plurality of first protrusions, and the second structural layer is composed of a plurality of second protrusions; The bottom of the second boss is provided with a chamfer structure between it and the ceramic substrate. The chamfer structure has an arc-shaped opening with a width of 1 to 1.5 mm. The ceramic matrix is ​​a porous silicon nitride ceramic or a quartz fiber reinforced quartz ceramic matrix composite material; The dielectric constant of the ceramic matrix is ​​2.9~3.3, the dielectric loss tangent is not greater than 0.008, and the total thickness of the ceramic matrix is ​​16.1~26.5mm; The thermal insulation material is connected to the first structural layer. The dielectric constant of the thermal insulation material is 1.1~1.4, the dielectric loss tangent is not greater than 0.008, and the thickness of the thermal insulation material is 4.8~5.2mm. The ceramic material is suitable for long-term use in high-temperature environments above 1400°C.

2. The method for preparing a microstructure-based ceramic material according to claim 1, characterized in that, The height H1 of the first boss is 6.3~7.3mm, the side length a1 of the top square is 3.4~3.8mm, the side length b1 of the bottom square is 5.3~6.3mm, and the period P1 is 6.9~7.1mm.

3. The method for preparing a microstructure-based ceramic material according to claim 1, characterized in that, The height H2 of the second boss is 4.9~5.3mm, the side length a2 of the top square is 3.1~4.1mm, the side length b2 of the bottom square is 4.9~5.1mm, and the period P2 is 6.9~7.1mm.

4. The method for preparing a microstructure-based ceramic material according to claim 1, characterized in that, The thermal insulation material is connected to the ceramic matrix by an adhesive, which is aluminum dihydrogen phosphate.

5. A ceramic material prepared by the method for preparing microstructure-based ceramic materials according to any one of claims 1-4, wherein the ceramic material has a transmittance of more than 70% in the range of 4-18 GHz.

6. The ceramic material according to claim 5 is used in a broadband radome.

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