CN110668836B

CN110668836B - Composite material for radome/antenna window and preparation method thereof

Info

Publication number: CN110668836B
Application number: CN201911017546.7A
Authority: CN
Inventors: 吴宝林; 侯振华
Original assignee: Jiangxi Jiajie Xinda New Material Technology Co ltd
Current assignee: Jiangxi Xinda Hangke New Material Technology Co ltd
Priority date: 2019-10-24
Filing date: 2019-10-24
Publication date: 2021-11-02
Anticipated expiration: 2039-10-24
Also published as: CN110668836A

Abstract

The invention discloses a SiO for a radar antenna housing/antenna window_2f/SiO₂The composite material and the preparation method thereof comprise the following preparation steps: preparation of chopped quartz fiber modified SiO_2f/SiO₂Composite material of SiO_2f/SiO₂The composite material is put into a chemical vapor deposition furnace, and boron trihalide and NH are introduced into the furnace under the vacuum condition₃And B (N (CH)₃)₂)₃The precursor gas is deposited to obtain BN modified SiO_2f/SiO₂A 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.

Description

Composite material for radome/antenna window and preparation method thereof

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, it is necessary to prepare a material having more excellent properties for satisfying the requirements of the radome/antenna windowSiO_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) 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 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 silica sol, so that the ceramic matrix can be effectively reinforcedStrength and toughness; 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:

(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.

Example 1

BN modified SiO for preparing radome/antenna window_2f/SiO₂A composite material comprising the steps of:

(1) heat treatment of the quartz fiber preform: heating the quartz fiber preform to 250 ℃ in an air environment for 1 hour, preserving heat for 2 hours, and cooling to room temperature along with the furnace;

(2) preparing a gel material: adding the heat-treated chopped quartz fiber with the length of 200 mu m into the silica sol, wherein the content is 5 wt%, and uniformly stirring; putting the prefabricated body into a silica sol solution, vacuumizing and maintaining the pressure for 0.5 hour; taking out, and drying in a muffle furnace for 4 hours at the temperature of 80 ℃ to obtain a gel material;

(3) putting the gel material obtained in the step (2) into a vacuum furnace, and introducing nitrogen at the flow rate of 50 ml/min; heating to 650 ℃ within 2 hours, preserving heat for 4 hours, cooling to room temperature within 4 hours, and measuring the density;

(4) repeating the step (3) until the density reaches 1.7g/cm³；

(5) Putting the product obtained in the step (4) into a chemical vapor deposition furnace, and vacuumizing; introducing boron trichloride and NH₃And B (N (CH)₃)₂)₃The mixed gas of (2) is used as a precursor reaction gas, and the mass ratio of the three gases is 3: 1: 1; introducing nitrogen as carrier gas; the gas flow of the precursor is 100ml/min, and the gas flow of the carrier gas is 20 ml/min; keeping the pressure in the furnace at 50 KPa; the furnace body is heated to 1000 ℃ for 2 hours and is kept warm for 0.5 hour, then the temperature is raised to 1400 ℃ for 1 hour, and the furnace body is cooled to room temperature for 4 hours and taken out.

Example 2

(1) heat treatment of the quartz fiber preform: heating the quartz fiber preform to 300 ℃ in an air environment for 2 hours, preserving the heat for 2 hours, and cooling the quartz fiber preform to room temperature along with a furnace;

(2) preparing a gel material: adding the heat-treated chopped quartz fibers with the length of 400 mu m into the silica sol, wherein the content is 8 wt%, and uniformly stirring; putting the prefabricated body into a silica sol solution, vacuumizing and maintaining the pressure for 1 hour; taking out, and drying in a muffle furnace for 8 hours at the temperature of 80 ℃ to obtain a gel material;

(3) putting the gel material obtained in the step (2) into a vacuum furnace, and introducing argon gas at the flow rate of 100 ml/min; heating to 800 ℃ within 4 hours, preserving the heat for 2 hours, cooling to room temperature within 2 hours, and measuring the density;

(4) repeating the step (3) until the density reaches 1.7g/cm 3;

(5) putting the product obtained in the step (4) into a chemical vapor deposition furnace, and vacuumizing; introducing boron trichloride and NH₃And B (N (CH)₃)₂)₃The mixed gas of (2) is used as a precursor reaction gas, and the mass ratio of the three gases is 4: 2: 1; introducing argon as carrier gas; the precursor gas flow is 150ml/min, and the carrier gas flow is 20 ml/min; maintaining the pressure in the furnace at 20 KPa; the furnace body is heated to 1200 ℃ for 4 hours and is kept warm for 1 hour, then the temperature is raised to 1400 ℃ for 2 hours, and the furnace body is cooled to room temperature for 6 hours and taken out.

Example 3

(1) heat treatment of the quartz fiber preform: heating the quartz fiber preform to 280 ℃ in an air environment for 1 hour, preserving heat for 1 hour, and cooling to room temperature along with the furnace;

(2) preparing a gel material: adding the heat-treated chopped quartz fiber with the length of 300 mu m into the silica sol, wherein the content is 10 wt.%, and uniformly stirring; putting the prefabricated body into a silica sol solution, vacuumizing and maintaining the pressure for 1 hour; taking out, and drying in a muffle furnace for 6 hours at the temperature of 80 ℃ to obtain a gel material;

(3) putting the gel material obtained in the step (2) into a vacuum furnace, and introducing argon gas at the flow rate of 80 ml/min; heating to 700 ℃ within 3 hours, preserving heat for 3 hours, cooling to room temperature within 3 hours, and measuring and calculating the density;

(4) repeating the step (3) until the density reaches 1.7g/cm³；

(5) Putting the product obtained in the step (4) into a chemical vapor deposition furnace, and vacuumizing; introducing boron trichloride and NH₃And B (N (CH)₃)₂)₃The mixed gas of (2) is used as a precursor reaction gas, and the mass ratio of the three gases is 2: 2: 1; introducing argon as carrier gas; precursor gasThe volume flow is 180ml/min, and the carrier gas flow is 20 ml/min; maintaining the pressure in the furnace at 40 KPa; the furnace body is heated to 1100 ℃ for 3 hours and is kept warm for 1 hour, then the temperature is heated to 1450 ℃ for 2 hours, and the furnace body is cooled to room temperature for 5 hours and taken out.

The flexural strength of the composite materials prepared in examples 1 to 3 was measured, the dielectric constant and dielectric loss of the composite materials at 10GHz were measured, and the strength retention of the composite materials after 50 thermal shock cycles of heat preservation at 1000 ℃ for 5min in cold water for 30min was measured, and the properties of the composite materials are shown in table 1.

TABLE 1 composite Properties

	Bending strength (MPa)	Dielectric constant at 10GHz	Dielectric loss	Strength Retention (%)
					Example 1	220	2.0	0.0017	76
Example 2	250	2.3	0.0011	82
					Example 3	270	2.5	0.0008	85

The radome/antenna window prepared by the embodiment of the invention has bending strength of more than 200MPa, dielectric constant of about 2.0-2.5 at 10GHz, dielectric loss of 0.005-0.020 and good anti-seismic performance, and meets the use requirements of high-speed aircrafts on radomes/antenna windows.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.

Claims

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

(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；

In the step (1), the quartz fiber prefabricated part is heated to the temperature of 250-300 ℃ for 1-2 hours during heat treatment, and then is naturally cooled to the room temperature after heat preservation for 1-2 hours;

the quartz fiber preform is 2D SiO_2fPreform, 2.5D SiO_2fPreform, 3D SiO_2fOne of the preforms; the length of the short-cut quartz fiber is 200-400 mu m;

the content of chopped quartz fibers in the silica sol is 5-10 wt.%;

the step of preparing the gel material in the step (1) comprises the following steps: 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;

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-;

in the deposition process of 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 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。

2. 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.

3. BN-modified SiO for radome/antenna windows prepared by the process according to any one of claims 1-2_2f/SiO₂A composite material.