阅读说明：本技术 雷达天线罩/天线窗用复合材料及其制备方法 (Composite material for radome/antenna window and preparation method thereof ) 是由 吴宝林 侯振华 于 2019-10-24 设计创作，主要内容包括：本发明公开了一种雷达天线罩/天线窗用SiO<Sub>2f</Sub>/SiO<Sub>2</Sub>复合材料及其制备方法,制备步骤包括：制备短切石英纤维改性的SiO<Sub>2f</Sub>/SiO<Sub>2</Sub>复合材料,将SiO<Sub>2f</Sub>/SiO<Sub>2</Sub>复合材料放入化学气相沉积炉,在真空条件下通入含有三卤化硼、NH<Sub>3</Sub>和B(N(CH<Sub>3</Sub>)<Sub>2</Sub>)<Sub>3</Sub>的先驱体气体,沉积即得到BN改性的SiO<Sub>2f</Sub>/SiO<Sub>2</Sub>复合材料。本发明制备得到的BN涂层力学性能好,介电性能优良,同时在天线罩/天线窗表面形成了压应力层,提高了雷达天线罩/天线窗的力学性能和抗热震性能。(The invention discloses a SiO for a radar antenna housing/antenna window 2f /SiO 2 The composite material and the preparation method thereof comprise the following preparation steps: preparation of chopped quartz fiber modified SiO 2f /SiO 2 Composite material of SiO 2f /SiO 2 The composite material is put into a chemical vapor deposition furnace, and boron trihalide and NH are introduced into the furnace under the vacuum condition 3 And B (N (CH) 3 ) 2 ) 3 A precursor gas of (2), depositing to obtainBN modified SiO 2f /SiO 2 A composite material. The BN coating prepared by the method has good mechanical property and excellent dielectric property, and meanwhile, a compressive stress layer is formed on the surface of the antenna housing/antenna window, so that the mechanical property and the thermal shock resistance of the radar antenna housing/antenna window are improved.)

1. SiO for radar antenna housing/antenna window_2f/SiO₂The preparation method of the composite material is characterized by comprising the following steps:

(1) carrying out heat treatment on the quartz fiber preform in an air environment; adding the chopped quartz fibers into the silica sol, uniformly stirring, then putting the quartz fiber preform into the silica sol, and carrying out vacuum pressure maintaining and drying to obtain a gel material;

(2) sintering the gel material in the protective gas atmosphere, and measuring and calculating the density of the obtained material; repeating the sintering step until the preset density is reached, thus obtaining the SiO_2f/SiO₂A composite material;

(3) mixing SiO_2f/SiO₂Putting the composite material into a chemical vapor deposition furnace, vacuumizing, introducing precursor gas and carrier gas, raising the temperature of a hearth to 1000-1200 ℃, preserving the temperature for 0.5-1 h, then raising the temperature to 1400-1450 ℃, and cooling to room temperature to finish deposition; the precursor gas contains boron trihalide, NH₃And B (N (CH)₃)₂)₃。

2. The radome/antenna window SiO of claim 1_2f/SiO₂The preparation method of the composite material is characterized in that in the step (1), the quartz fiber prefabricated member is heated to 250-300 ℃ for 1-2 hours during heat treatment, is kept at the temperature for 1-2 hours, and is naturally cooled to room temperature.

3. The radome/antenna window SiO of claim 1_2f/SiO₂The preparation method of the composite material is characterized in that the quartz fiber preform is at least 2D SiO_2fPreform, 2.5D SiO_2fPreform, 3D SiO_2fAnd (4) prefabricating.

4. The radome/antenna window SiO of claim 1_2f/SiO₂A method for preparing a composite material, characterized in that the chopped stone isThe length of the quartz fiber is 200-400 mu m; the content of the chopped quartz fibers in the silica sol is 5-10 wt.%.

5. The radome/antenna window SiO of claim 1_2f/SiO₂The preparation method of the composite material is characterized in that the step of preparing the gel material in the step (1) comprises the following steps: and (3) putting the quartz fiber preform into a silica sol solution, vacuumizing and maintaining the pressure for 0.5-1 hour, and drying in a muffle furnace at the temperature of 80 ℃ for 4-8 hours.

6. The radome/antenna window SiO of claim 1_2f/SiO₂The preparation method of the composite material is characterized in that in the step (2), the protective gas is nitrogen or argon; the flow rate of the protective gas is 50-100 ml/min.

7. The radome/antenna window SiO of claim 1_2f/SiO₂The preparation method of the composite material is characterized in that the temperature rise procedure during sintering in the step (2) is as follows: raising the temperature to 650-800 ℃ for 2-4 hours, preserving the heat for 2-4 hours, and then cooling to room temperature for 2-4 hours; the preset density is 1.7g/cm³。

8. The radome/antenna window SiO of claim 1_2f/SiO₂A process for the preparation of a composite material, characterized in that the precursor comprises boron trihalide, NH3 and B (N (CH)₃)₂)₃The amount ratio of the substances (2) to (5): (1-2): 1; the carrier gas is one or more than two mixed gases of nitrogen, hydrogen and argon; the flow ratio of the precursor to the carrier gas is (5-10): 1, and the total flow rate of the precursor gas and the carrier gas is 100-.

9. The radome/antenna window SiO of claim 1_2f/SiO₂The preparation method of the composite material is characterized in that in the deposition process in the step (3), the pressure in the furnace is controlled to be 20-50 KPa; heating the furnace body to 1000-1200 ℃ within 2-4 hours, preserving the heat for 0.5-1 hour, heating the furnace body to 1400-1450 ℃ within 1-2 hours, and cooling the furnace body to room temperature within 4-6 hours to obtain BN modified SiO_2f/SiO₂A composite material.

10. BN-modified SiO for radome/antenna windows prepared by the process according to any one of claims 1 to 9_2f/SiO₂A composite material.

Technical Field

The invention belongs to the technical field of materials, and particularly relates to high-strength high-temperature-resistant SiO for a radome/antenna window_2f/SiO₂Composite materials and methods for making the same.

Background

The radome/antenna window is arranged on the head or the side face of the high-speed aircraft and used for protecting equipment for normal work of a communication system on the aircraft and ensuring signal transmission, and the composite material for the radome/antenna window is generally required to have good mechanical property, thermal property and dielectric property. With the increasing speed of the aircraft, the high-mach-number aircraft puts higher requirements on the performance of the radome/antenna window. At present, the performance of the radome/antenna window is improved mainly from the aspects of selection of raw materials, optimization of structure and the like. The ceramic material is regarded as an ideal material for the radome/antenna window due to the properties of high strength, high temperature resistance and the like. In particular SiO_2f/SiO₂The ceramic matrix composite is used as one of the fields of aerospace thermal protection and wave-transparent composite materials, and is most mature and widely applied at present.

However, SiO_2f/SiO₂Ceramic matrix composites also suffer from a number of disadvantages, such as SiO_2f/SiO₂The matrix of the ceramic matrix composite is made of silica sol and is a porous structure containing a silicon-oxygen bond irregular network structure, and meanwhile, a large amount of silicon hydroxyl exists on the surface of the matrix, so that the activity is high, the moisture absorption rate is up to 5-10%, the influence on the dielectric property of the composite is large, and the density of the matrix of the porous structure is low, so that the mechanical property and the ablation property of the composite are seriously influenced. In addition, the poor temperature resistance of the quartz fiber causes SiO_2f/SiO₂The ceramic matrix composite material is far from reaching SiO₂Sintering temperature of the particles so that SiO_2f/SiO₂The mechanical strength of the ceramic matrix composite is poor. Therefore, for SiO_2f/SiO₂It is important that the ceramic matrix composite be modified to meet the requirements of high mach aircraft.

Boron Nitride (BN), an important ceramic as a nitride, has excellent thermal and dielectric properties, a high decomposition temperature, and excellent thermal and electrical property stability over a wide temperature range. In SiO_2f/SiO₂The BN matrix is introduced into the composite material to coat SiO to a great extent₂The content of silicon hydroxyl on the surface of the substrate is reduced, the moisture absorption rate of the substrate is effectively reduced, and the overall strength of the material is improved so as to meet the requirement of an aircraft with high Mach number.

SiO_2f/SiO₂The method for introducing BN into the composite material mainly comprises a high-temperature powder sintering method and a PIP (pre-sintering and Pyrolysis) method which takes borazane as a precursor, the high-temperature sintering method is early developed, but the exertion of the excellent myocardial infarction of BN is more limited, while the PIP method has numerous advantages of precursor designability, good manufacturability, processability and the like, but the PIP method has great dependence on the synthesis technology of the precursor, complex equipment and very high cost. Therefore, there is a need to prepare SiO with better performance for satisfying the radar antenna cover/antenna window_2f/SiO₂A composite material.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides SiO for a radar antenna housing/antenna window_2f/SiO₂The preparation method of the composite material is characterized in that the chopped quartz fiber is introduced into the silica sol to enhance the strength and the toughness of the ceramic matrix, and a Chemical Vapor Deposition (CVD) method is adopted to prepare the SiO ceramic with the high toughness and the high strength_2f/SiO₂And a BN coating is obtained by deposition growth on the surface of the composite material matrix. The BN coating has good mechanical property and excellent dielectric property, and a pressure stress layer is formed on the surface of the antenna housing/antenna window, so that the mechanical property and the thermal shock resistance of the radar antenna housing/antenna window are effectively improved.

In order to solve the technical problems, the invention adopts the following technical scheme:

SiO for radar antenna housing/antenna window_2f/SiO₂The preparation method of the composite material comprises the following steps:

(1) carrying out heat treatment on the quartz fiber preform in an air environment; adding the chopped quartz fibers into the silica sol, uniformly stirring, then putting the quartz fiber preform into the silica sol, and carrying out vacuum pressure maintaining and drying to obtain a gel material;

(2) protection ofSintering the gel material in a gas atmosphere, and measuring and calculating the density of the obtained material; repeating the sintering step until the preset density is reached, thus obtaining the SiO_2f/SiO₂A composite material;

(3) mixing SiO_2f/SiO₂Putting the composite material into a chemical vapor deposition furnace, vacuumizing, introducing precursor gas and carrier gas, raising the temperature of a hearth to 1000-1200 ℃, preserving the temperature for 0.5-1 h, then raising the temperature to 1400-1450 ℃, and cooling to room temperature to finish deposition; the precursor gas contains boron trihalide, NH₃And B (N (CH)₃)₂)₃. The boron trihalide is boron trifluoride or boron trichloride.

Preferably, in the step (1), the quartz fiber preform is heated to 250-300 ℃ for 1-2 hours and then is kept at the temperature for 1-2 hours during the heat treatment, and then is naturally cooled to room temperature.

Preferably, the quartz fiber preform is at least 2D SiO_2fPreform, 2.5D SiO_2fPreform, 3D SiO_2fAnd (4) prefabricating.

Preferably, the length of the chopped quartz fibers is 200-400 μm; the content of the chopped quartz fibers in the silica sol is 5-10 wt.%.

Preferably, the step of preparing the gel material in step (1) comprises: and (3) putting the quartz fiber preform into a silica sol solution, vacuumizing and maintaining the pressure for 0.5-1 hour, and drying in a muffle furnace at the temperature of 80 ℃ for 4-8 hours.

Preferably, in the step (2), the protective gas is nitrogen or argon; the flow rate of the protective gas is 50-100 ml/min.

Preferably, the temperature raising procedure in the sintering in the step (2) is: raising the temperature to 650-800 ℃ for 2-4 hours, preserving the heat for 2-4 hours, and then cooling to room temperature for 2-4 hours; the preset density is 1.7g/cm³。

Preferably, the precursor has boron trihalide, NH₃And B (N (CH)₃)₂)₃The amount ratio of the substances (2) to (5): (1-2): 1; the carrier gas is one or more than two mixed gases of nitrogen, hydrogen and argon; the flow ratio of the precursor to the carrier gas is (5-10):1, and the total flow rate of the precursor gas and the carrier gas is 100-.

Preferably, during the deposition in the step (3), the pressure in the furnace is controlled to be 20-50 KPa; heating the furnace body to 1000-1200 ℃ within 2-4 hours, preserving the heat for 0.5-1 hour, heating the furnace body to 1400-1450 ℃ within 1-2 hours, and cooling the furnace body to room temperature within 4-6 hours to obtain BN modified SiO_2f/SiO₂A composite material.

The invention also provides BN modified SiO for the radome/antenna window prepared by the method_2f/SiO₂A composite material.

The invention has the beneficial effects that:

the invention prepares SiO_2f/SiO₂When the composite material is used, the chopped quartz fibers are introduced into the silica sol, so that the strength and toughness of the ceramic matrix can be effectively enhanced; simultaneously on SiO by chemical vapor deposition_2f/SiO₂The BN coating is obtained by deposition growth of the composite material, the obtained BN coating is good in mechanical property and excellent in dielectric property, and meanwhile, a pressure stress layer is formed on the surface of the antenna housing/antenna window, so that the mechanical property and the thermal shock resistance of the radar antenna housing/antenna window are improved.

Drawings

In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.

FIG. 1 is a graph showing the effect of fiber length on the bending strength of a material at different fiber loadings;

FIG. 2 is a graph showing the effect of fiber length on the dielectric constant of a material at different fiber loadings;

FIG. 3 is a graph showing the effect of fiber length on dielectric loss of a material at different fiber loadings.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.

It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the invention pertains.

The experimental procedures in the following examples are conventional unless otherwise specified. The test materials used in the following examples were purchased from a conventional biochemical reagent store unless otherwise specified. In the quantitative tests in the following examples, three replicates were set, and the data are the mean or the mean ± standard deviation of the three replicates.

The invention relates to a SiO for a radar antenna housing/antenna window_2f/SiO₂The preparation method of the composite material comprises the following steps:

(1) carrying out heat treatment on the quartz fiber preform in an air environment; adding the chopped quartz fibers into the silica sol, uniformly stirring, then putting the quartz fiber preform into the silica sol, and carrying out vacuum pressure maintaining and drying to obtain a gel material;

(2) sintering the gel material in the protective gas atmosphere, and measuring and calculating the density of the obtained material; repeating the sintering step until the preset density is reached, thus obtaining the SiO_2f/SiO₂A composite material;

(3) mixing SiO_2f/SiO₂Putting the composite material into a chemical vapor deposition furnace, vacuumizing, introducing precursor gas and carrier gas, raising the temperature of a hearth to 1000-1200 ℃, preserving the temperature for 0.5-1 h, then raising the temperature to 1400-1450 ℃, and cooling to room temperature to finish deposition; the precursor gas contains boron trihalide, NH₃And B (N (CH)₃)₂)₃。

The invention utilizes BN to modify SiO_2f/SiO₂The BN-SiO obtained by different fiber mixing amount pairs is also researched in the process of the composite material_2f/SiO₂The effect of the properties of the composite.

As can be seen from FIG. 1, when the fiber content is less than 5%, the bending strength of the composite material is less than 200 MPa; when the fiber content is more than 15%, the strength of the composite material is still less than 200 MPa; as the fiber length increases, the composite material generally exhibits a tendency to increase and then decrease in flexural strength. The preferred range is 200-400 μm.

As can be seen from FIG. 2, the dielectric constant of the material does not change significantly with the length of the fiber under the same fiber content. However, as the amount of the fiber is increased, the dielectric constant of the material is slightly increased. When the fiber content is less than 10%, the dielectric constant is substantially less than 2.5.

As can be seen from FIG. 3, the dielectric loss fluctuates in the range of 0.005 to 0.20, satisfying the use requirements.