阅读说明：本技术 氧化硅短纤维模压陶瓷天线窗复合材料及其制备方法 (Silicon oxide short fiber die-pressed ceramic antenna window composite material and preparation method thereof ) 是由 刘俊君 佘平江 郭培江 张雨葳 于 2020-12-18 设计创作，主要内容包括：本发明公开了一种氧化硅短纤维模压陶瓷天线窗复合材料及其制备方法,属于陶瓷材料技术领域。它包括如下步骤：1)制备硅凝胶；2)物料混匀；3)模压处理；4)预干燥处理；5)第一次高温处理；6)凝胶浸渍处理；7)第二次高温处理。本发明在步骤1)中采用硅溶胶用作粘接剂,在不引入其他杂质及不破坏纤维本身结构前提下使氧化硅短纤维与硅凝胶结合充分,继续经模具模压成型后热处理得到坯体,该坯体在步骤6)的浸渍复合处理中实现了对胚体表面微小凹坑的修补,使得制备的复合材料不仅密度相对较高,而且表面质量好。(The invention discloses a silicon oxide short fiber die-pressed ceramic antenna window composite material and a preparation method thereof, belonging to the technical field of ceramic materials. It comprises the following steps: 1) preparing a silica gel; 2) uniformly mixing the materials; 3) carrying out mould pressing treatment; 4) pre-drying treatment; 5) carrying out high-temperature treatment for the first time; 6) gel dipping treatment; 7) and (5) performing high-temperature treatment for the second time. According to the invention, silica sol is used as an adhesive in the step 1), silica short fibers and silica gel are fully combined on the premise of not introducing other impurities and not damaging the structure of the fiber, a blank is obtained by heat treatment after mould compression molding is continuously carried out on the silica short fibers and the silica gel, and the blank realizes repair of tiny pits on the surface of the blank in the dipping composite treatment in the step 6), so that the prepared composite material has relatively high density and good surface quality.)

1. A preparation method of a silicon oxide short fiber mould pressing ceramic antenna window composite material is characterized by comprising the following steps:

1) preparing a silica gel: heating silica sol with solid content of 38-42% and particle size of 7-20 nm in water bath at 80-90 ℃ for a period of time to obtain silica gel;

2) material mixing: smashing the silica gel prepared in the step 1) to form uniform particles with the particle size of less than or equal to 2mm, uniformly mixing the particles with silicon oxide short fibers with the length of 2-4 mm according to the mass ratio of 1 (1.3-1.4), and then placing the mixture in a vacuum bag to maintain the pressure for a period of time in a negative pressure environment;

3) and (3) mould pressing treatment: placing the uniformly mixed material obtained in the step 2) into a mould pressing tool, controlling the pressure to be 30-40 MPa, maintaining the pressure at 40-50 ℃ for 1-1.5 h, and demoulding to obtain a mould;

4) pre-drying treatment: placing the model in the step 3) into a drying oven, drying for 1-2 h at 40-50 ℃, and then heating to 100-120 ℃ for drying for 2-3 h to obtain a mould pressing ceramic blank;

5) high-temperature treatment for the first time: placing the die pressing ceramic blank in the step 4) into a high temperature furnace, heating to 650-800 ℃ in a short time, preserving heat for 1-3 hours, and cooling to room temperature;

6) gel impregnation treatment: placing the blank obtained in the step 5) into silica sol with the solid content of 21-25% and the particle size of 7-20 nm for dipping treatment for 6-8 h, and controlling the dipping treatment temperature to be 80-90 ℃;

7) and (3) second high-temperature treatment: and (3) placing the blank treated in the step 6) in a high-temperature furnace, heating to 110-130 ℃, preserving heat for 1-3 hours, then quickly heating to 1000-1400 ℃, preserving heat for 1-3 hours, cooling to room temperature, and taking out to obtain the silicon oxide short fiber molded ceramic antenna window composite material.

2. The method for preparing the silica short fiber molded ceramic antenna window composite material as claimed in claim 1, wherein in the step 1), the silica sol has a pH value of 2-5 at 20 ℃ and a dynamic viscosity of not more than 15 x 10 at 25 ℃^-3Pa·S；

And heating the silica sol in a water bath at 80-90 ℃ for 20-24 h to obtain the silica gel, wherein the water content of the silica gel is 40-60%.

3. The method for preparing the silica short fiber molded ceramic antenna window composite material as claimed in claim 1, wherein in the step 5), the silica sol has a pH value of 2-4 at 20 ℃ and a dynamic viscosity of 12 x 10 or less at 25 ℃^-3Pa·S。

4. The preparation method of the silicon oxide short fiber die-pressed ceramic antenna window composite material as claimed in any one of claims 1 to 3, wherein the linear density of the silicon oxide short fiber is 190 ± 8tex, the mass percentage content of silicon dioxide is not less than 99.90%, and the breaking strength is not less than 60N.

5. The preparation method of the silicon oxide short fiber molded ceramic antenna window composite material as claimed in claim 1, wherein in the step 2), the mass ratio of the silica gel to the silicon oxide short fiber is 1 (1.33-1.4).

6. The method for preparing the silicon oxide short fiber molded ceramic antenna window composite material according to claim 5, wherein in the step 2), the negative pressure environment is-60 to-80 kPa, and the pressure is maintained for 20 to 30 min.

7. The method for preparing the silicon oxide short fiber molded ceramic antenna window composite material as claimed in claim 1, wherein in the step 5), the temperature rise rate is controlled to be 2-5 ℃/min, and the temperature is raised to 700-750 ℃.

8. The preparation method of the silicon oxide short fiber molded ceramic antenna window composite material according to claim 1, wherein in the step 7), the temperature rise speed is controlled to be 2-3 ℃/min, the temperature is raised to 110-120 ℃, the temperature is kept for 1-3 h, and then the temperature rise speed is controlled to be 3-5 ℃/min, and the temperature is raised to 1100-1300 ℃.

9. A silicon oxide short fiber molded ceramic antenna window composite material prepared by the preparation method of any one of claims 1 to 8.

10. The silica staple fiber molded ceramic antenna window composite of claim 9, wherein the density of the composite is 1.80 to 1.90g/cm³The bending strength is 60 to 80MPa, the tensile strength is 45 to 60MPa, the thermal conductivity is 0.50 to 0.60W/m.k, and the loss tangent is 0.00035 to 0.00055.

Technical Field

The invention relates to a material for a space flight vehicle, belongs to the technical field of ceramic materials, and particularly relates to a silicon oxide short fiber die-pressed ceramic antenna window composite material and a preparation method thereof.

Background

The antenna window is used as a communication window for controlling the missile and is a key part for ensuring the normal work of a radar system. With the development of aerospace technology, the aerodynamic appearance of an aircraft presents a special-shaped structure, and the development trend of the special-shaped structure of an antenna window with wave-transmitting, heat-insulating and bearing functions also appears. The high-Mach aircraft mostly adopts the ceramic-based wave-transmitting, wherein, the quartz fiber reinforced quartz composite ceramic material is most widely applied. Most of the traditional forming methods of quartz composite ceramic antenna windows are that quartz fibers are woven into fiber flat fabrics (such as 2.5D, needle punching, sewing and the like), then silica sol is impregnated into the fiber flat fabrics, the fiber flat fabrics are sintered into flat plates, and then the flat plates are machined into antenna window products with special-shaped structures.

The dipping composite molding needs to dip and compound the fiber woven body for multiple times, the blank needs to be machined, the production period is long, and the method is very unfavorable for developing antenna window products with pressed nodes. And the cost of the braid is high, which is not beneficial to mass production. In addition, quartz fibers are prone to fracture and tear during processing, resulting in poor image processing appearance.

Disclosure of Invention

In order to solve the technical problems, the invention discloses a silicon oxide short fiber die-pressed ceramic antenna window composite material and a preparation method thereof.

In order to realize the purpose, the invention discloses a preparation method of a silicon oxide short fiber mould pressing ceramic antenna window composite material, which comprises the following steps:

1) preparing a silica gel: heating silica sol with solid content of 38-42% and particle size of 7-20 nm in water bath at 80-90 ℃ for a period of time to obtain silica gel;

2) material mixing: smashing the silica gel prepared in the step 1) to form uniform particles with the particle size of less than or equal to 2mm, uniformly mixing the particles with silicon oxide short fibers with the length of 2-4 mm according to the mass ratio of 1 (1.3-1.4), and then placing the mixture in a vacuum bag to maintain the pressure for a period of time in a negative pressure environment;

3) and (3) mould pressing treatment: placing the uniformly mixed material obtained in the step 2) into a mould pressing tool, controlling the pressure to be 30-40 MPa, maintaining the pressure at 40-50 ℃ for 1-1.5 h, and demoulding to obtain a mould;

4) pre-drying treatment: placing the model in the step 3) into a drying oven, drying for 1-2 h at 40-50 ℃, and then heating to 100-120 ℃ for drying for 2-3 h to obtain a mould pressing ceramic blank;

5) high-temperature treatment for the first time: placing the die pressing ceramic blank in the step 4) into a high temperature furnace, heating to 650-800 ℃ in a short time, preserving heat for 1-3 hours, and cooling to room temperature;

6) gel impregnation treatment: placing the blank obtained in the step 5) into silica sol with the solid content of 21-25% and the particle size of 7-20 nm for dipping treatment for 6-8 h, and controlling the dipping treatment temperature to be 80-90 ℃;

7) and (3) second high-temperature treatment: and (3) placing the blank treated in the step 6) in a high-temperature furnace, firstly heating to 110-130 ℃, preserving heat for 1-3 hours, then quickly heating to 1000-1400 ℃, preserving heat for 1-3 hours, cooling to room temperature, and taking out to obtain the silicon oxide short fiber molded ceramic antenna window composite material.

Further, in the step 1), the pH value of the silica sol at 20 ℃ is 2-5, and the dynamic viscosity at 25 ℃ is not more than 15 multiplied by 10^-3Pa·S；

And heating the silica sol in a water bath at 80-90 ℃ for 20-24 h to obtain the silica gel, wherein the water content of the silica gel is 40-60%.

Further, in the step 5), the pH value of the silica sol at 20 ℃ is 2-4, and the dynamic viscosity at 25 ℃ is not more than 12 multiplied by 10^-3Pa·S。

Further, the linear density of the silicon oxide short fiber is 190 plus or minus 8tex, the mass percentage content of silicon dioxide is more than or equal to 99.90%, and the breaking strength is more than or equal to 60N. And if the surface of the silicon oxide short fiber contains the sizing agent, the silicon oxide short fiber needs to be heated to 380 ℃ for treatment for 2 hours before use so as to remove the sizing agent.

Further, in the step 2), the mass ratio of the silica gel to the short silica fiber is 1 (1.33-1.4).

Further, in the step 2), the negative pressure environment is-60 to-80 kPa, and the pressure is maintained for 20 to 30 min.

Further, in the step 5), the temperature is raised to 700-750 ℃ while controlling the temperature raising speed to 2-5 ℃/min.

Further, in the step 7), firstly, controlling the heating rate to be 2-3 ℃/min, heating to 110-120 ℃, preserving heat for 1-3 h, and then controlling the heating rate to be 3-5 ℃/min, and heating to 1100-1300 ℃.

In addition, the invention also discloses a silicon oxide short fiber die-pressed ceramic antenna window composite material which is prepared by adopting the preparation method.

Further, the density of the composite material is 1.80-1.90 g/cm³The bending strength is 60 to 80MPa, the tensile strength is 45 to 60MPa, the thermal conductivity is 0.50 to 0.60W/m.k, and the loss tangent is 0.00035 to 0.00055.

Has the advantages that:

1. in the preparation technology of this application design, make the bonding agent after carrying out the preliminary treatment with the silica sol, under the prerequisite that does not introduce other impurity, mix according to appointed proportion with quartz short fiber, obtain the mould pressing premix, put into the vacuum bag pressurization processing with the premix tiling, wherein silicon oxide short fiber structure itself can not change, if can not cause the fracture of silicon oxide short fiber, tear etc. simultaneously, the silica gel particulate matter is in the same place each silicon oxide short fiber cross-linking as the binder, form the structure of fusing into one, be favorable to improving combined material's intensity.

2. In the preparation process designed by the application, the treated premix is filled into a mould pressing die to be pressurized at a constant temperature, a blank is obtained by heat treatment after demoulding, and the blank is subjected to impregnation compounding and heat treatment, so that the compactness, the apparent quality and the structural strength of a product are improved.

3. The preparation technology designed by the application is simple, the processing efficiency is high, the product density is relatively high, and the product formability is good.

4. The density of the product prepared by the method is 1.80-1.90 g/cm³The bending strength is 60-80 Mpa, the tensile strength is 45-60 Mpa, the thermal conductivity is 0.50-0.60W/m.k, and the loss tangent is 0.00035-0.00055, so that the antenna window meets the quality requirements of antenna window products.

Detailed Description

The invention provides a silicon oxide short fiber die-pressing ceramic antenna window composite material and a preparation method thereof, aiming at solving the technical problems that the existing antenna window processing technology is complicated, the production period is long, and the structure of the material is easy to change in the processing process.

Specifically, the preparation method of the silicon oxide short fiber die-pressed ceramic antenna window composite material comprises the following steps:

1) preparing a silica gel: heating silica sol with solid content of 38-42% and particle size of 7-20 nm in water bath at 80-90 ℃ for a period of time to obtain silica gel; meanwhile, the invention also controls the pH value of the silica sol to be 2-5 at 20 ℃, and the dynamic viscosity of the silica sol to be not more than 15 multiplied by 10 at 25 DEG C^-3Pa.S; the silica sol with the parameters has small particle size and stable chemical property on the premise of relatively high solid content, and the obtained silica gel has good bonding effect; in addition, the silicon gel is heated in a water bath for 20-24 hours to be changed into silicon gel, and in order to ensure that the silicon gel can better play a role of an adhesive in the subsequent compounding process with the silicon oxide short fibers, the water content of the silicon gel is controlled to be 40-60%.

2) Material mixing: smashing the silica gel prepared in the step 1) to form uniform particles with the particle size of less than or equal to 2mm, uniformly mixing the particles with silicon oxide short fibers with the length of 2-4 mm according to the mass ratio of 1 (1.3-1.4), and then placing the mixture in a vacuum bag to maintain the pressure for a period of time in a negative pressure environment;

the linear density of the selected silicon oxide short fiber is 190 plus or minus 8tex, the content of silicon dioxide is more than or equal to 99.90 percent, and the breaking strength is more than or equal to 60N. The silicon oxide short fiber can be well crosslinked under the bonding action of silicon gel. Wherein, the content of silicon dioxide in the silicon oxide short fiber is not more than 100 percent by mass, and the breaking strength is not more than 80N.

The mass ratio of the silica gel to the short silica fiber is preferably 1 (1.33-1.4). And keeping the pressure of the mashed silicon gel particles and the silicon oxide short fibers for 20-30 min in a negative pressure environment of-60 to-80 kPa, wherein in the treatment process of the step, the structure of the silicon oxide short fibers cannot be changed, such as fracture, tearing and the like of the silicon oxide short fibers cannot be caused, and meanwhile, the silicon gel particles are used as a binder to crosslink the silicon oxide short fibers together to form an integrated structure, so that the strength of the composite material is improved.

3) And (3) mould pressing treatment: placing the uniformly mixed material obtained in the step 2) into a mould pressing tool, controlling the pressure to be 30-40 MPa, maintaining the pressure at 40-50 ℃ for 1-1.5 h, and demoulding to obtain a mould; the mould pressing tool selected by the invention is the existing tool, the structure of the mould pressing tool is not specially limited, meanwhile, the common release agent is uniformly coated on the peripheral inner walls of the mould pressing tool, the mixed material is placed in the mould pressing tool, the silicon oxide short fibers and the silicon gel particles have good fluidity, the net size forming of the antenna window is facilitated, meanwhile, the silicon oxide short fibers are uniformly distributed, and the structural strength of the formed model is enhanced.

4) Pre-drying treatment: placing the model in the step 3) into a drying oven, drying for 1-2 h at 40-50 ℃, and then heating to 100-120 ℃ for drying for 2-3 h to obtain a mould pressing ceramic blank;

the drying box is preferably an electric heating air blowing drying box.

5) High-temperature treatment for the first time: placing the die pressing ceramic blank in the step 4) into a high temperature furnace, heating to 650-800 ℃ in a short time, preserving heat for 1-3 hours, and cooling to room temperature;

the temperature rise speed is preferably controlled to be 2-5 ℃/min, and the temperature is raised to 700-750 ℃.

6) Gel impregnation treatment: placing the blank obtained in the step 5) into silica sol with the solid content of 21-25% and the particle size of 7-20 nm for dipping treatment for 6-8 h, and controlling the dipping treatment temperature to be 80-90 ℃; wherein the pH value of the silica sol at 20 ℃ is controlled to be 2-4, and the dynamic viscosity at 25 ℃ is not more than 12 multiplied by 10^-3Pa.S, the silica sol with the parameters has small particle size and low viscosity, is beneficial to the silica sol colloidal particles to penetrate through micropores on the surface of the ceramic blank, and is more stably combined with the interface of the ceramic blank. In addition, the solid content of the silica sol used in the step is lower than that in the step 1), the blank body is placed in the silica sol to be fully soaked, the soaking efficiency is improved at a certain glue temperature until the silica sol becomes silica gel, the repair of tiny pits on the surface of the blank body can be realized, and the air holes in the composite material are finer and more uniform,the surface quality is better.

7) And (3) second high-temperature treatment: and (3) placing the blank treated in the step 6) in a high-temperature furnace, firstly heating to 110-130 ℃, preserving heat for 1-3 hours, then quickly heating to 1000-1400 ℃, preserving heat for 1-3 hours, cooling to room temperature, and taking out to obtain the silicon oxide short fiber molded ceramic antenna window composite material.

The method preferably comprises the steps of firstly controlling the heating speed to be 2-3 ℃/min, heating to 110-120 ℃, keeping the temperature for 1-3 h, and then controlling the heating speed to be 3-5 ℃/min, and heating to 1100-1300 ℃. The processing of the process steps is characterized in that low-temperature heat preservation is firstly carried out, so that the dipped glue solution is fully combined with the matrix, then the temperature is raised at a constant speed, and then high-temperature heat preservation is carried out for sintering, thereby being beneficial to improving the strength of the blank.

The invention also preferably selects the high-temperature furnace in the step 5) and the step 7) as a muffle furnace.

The density of the composite material prepared by the preparation process is 1.80-1.90 g/cm³The bending strength is 60 to 80MPa, the tensile strength is 45 to 60MPa, the thermal conductivity is 0.50 to 0.60W/m.k, and the loss tangent is 0.00035 to 0.00055.

In order to better explain the present invention, the following detailed description is given in conjunction with specific examples.

Example 1

The embodiment discloses a silicon oxide short fiber die-pressed ceramic antenna window composite material, which comprises the following preparation steps:

1) preparing a silica gel: taking the solid content of 38 percent, the particle diameter of 7-10 nm, the pH value of 2 at 20 ℃ and the dynamic viscosity of 15 multiplied by 10 at 25 DEG C^-3Heating the Pa.S silica sol in a water bath at 80 ℃ for 24h to convert the silica sol into silica gel;

2) material mixing: smashing the silica gel prepared in the step 1) to form uniform particles with the particle size of about 2mm, uniformly mixing the particles with silicon oxide short fibers with the length of 2mm according to the mass ratio of 1:1.3, placing the mixture in a vacuum bag, and maintaining the pressure for 30min under the negative pressure environment of-60 kPa;

3) and (3) mould pressing treatment: placing the uniformly mixed material obtained in the step 2) into a mould pressing tool, controlling the pressure to be 30MPa, maintaining the pressure at 40 ℃ for 1.5h, and demoulding to obtain a mould;

4) pre-drying treatment: placing the model in the step 3) in an electric heating blast drying oven, drying for 2h at 40 ℃, and then heating to 100 ℃ and drying for 3h to obtain a mould pressing ceramic blank;

5) high-temperature treatment for the first time: placing the molded ceramic blank in the step 4) in a high-temperature furnace, controlling the heating rate to be 2 ℃/min, heating to 650 ℃, preserving heat for 3h, and then cooling to room temperature;

6) gel impregnation treatment: placing the embryo body obtained in the step 5) into a container with the solid content of 21%, the particle size of 7-10 nm, the pH value of 2 at 20 ℃ and the dynamic viscosity of 12 multiplied by 10 at 25 DEG C^-3Soaking in Pa & S silica sol for 8 h; wherein the temperature of the silica sol is 80 ℃;

7) and (3) second high-temperature treatment: and (3) placing the blank treated in the step 6) into a high-temperature furnace, firstly controlling the heating rate to be 2 ℃/min, heating to 110 ℃, preserving heat for 3h, then controlling the heating rate to be 5 ℃/min, heating to 1400 ℃, preserving heat for 3h, cooling to room temperature, and taking out to obtain the silicon oxide short fiber mould pressing ceramic antenna window composite material.

The material prepared by the embodiment has good surface quality, and does not have the conditions of pits, slag falling and the like. The properties of the test specimens were tested and the results are shown in Table 1.

Table 1 composite Properties List

Example 2

The embodiment discloses a silicon oxide short fiber die-pressed ceramic antenna window composite material, which comprises the following preparation steps:

1) preparing a silica gel: taking the solid content of 40 percent, the particle diameter of 10-15 nm, the pH value of 4 at 20 ℃ and the dynamic viscosity of 10 multiplied by 10 at 25 DEG C^-3Heating the Pa.S silica sol in a water bath at 90 ℃ for 20h to convert the silica sol into silica gel;

2) material mixing: smashing the silica gel prepared in the step 1) to form uniform particles with the particle size of about 2mm, uniformly mixing the particles with silicon oxide short fibers with the length of 2mm according to the mass ratio of 1:1.3, placing the mixture in a vacuum bag, and maintaining the pressure for 30min under the negative pressure environment of-60 kPa;

3) and (3) mould pressing treatment: placing the uniformly mixed material obtained in the step 2) into a mould pressing tool, controlling the pressure to be 30MPa, maintaining the pressure at 40 ℃ for 1.5h, and demoulding to obtain a mould;

4) pre-drying treatment: placing the model in the step 3) in an electric heating blast drying oven, drying for 2h at 40 ℃, and then heating to 100 ℃ and drying for 3h to obtain a mould pressing ceramic blank;

5) high-temperature treatment for the first time: placing the molded ceramic blank in the step 4) in a high-temperature furnace, controlling the heating rate to be 2 ℃/min, heating to 650 ℃, preserving heat for 3h, and then cooling to room temperature;

6) gel impregnation treatment: placing the embryo body obtained in the step 5) in a reactor with the solid content of 23%, the particle size of 10-15 nm, the pH value of 3 at 20 ℃ and the dynamic viscosity of 10 multiplied by 10 at 25 DEG C^-3Soaking in Pa & S silica sol for 6 h; wherein the temperature of the silica sol is 90 ℃;

7) and (3) second high-temperature treatment: and (3) placing the blank treated in the step 6) into a high-temperature furnace, firstly controlling the heating rate to be 2 ℃/min, heating to 110 ℃, preserving heat for 3h, then controlling the heating rate to be 5 ℃/min, heating to 1400 ℃, preserving heat for 3h, cooling to room temperature, and taking out to obtain the silicon oxide short fiber mould pressing ceramic antenna window composite material.

The material prepared by the embodiment has good surface quality, and does not have the conditions of pits, slag falling and the like. The properties of the test specimens were tested and the results are shown in Table 2.

Table 2 composite properties tabulation

Example 3

The embodiment discloses a silicon oxide short fiber die-pressed ceramic antenna window composite material, which comprises the following preparation steps:

1) preparing a silica gel: taking the solid content of 42 percent, the particle diameter of 15-20 nm, the pH value of 5 at 20 ℃ and the dynamic viscosity of 5 multiplied by 10 at 25 DEG C^-3Heating Pa.S silica sol in 90 deg.C water bath for 20 hr to changeIs a silica gel;

2) material mixing: smashing the silica gel prepared in the step 1) to form uniform particles with the particle size of about 2mm, uniformly mixing the particles with silicon oxide short fibers with the length of 2mm according to the mass ratio of 1:1.3, placing the mixture in a vacuum bag, and maintaining the pressure for 30min under the negative pressure environment of-60 kPa;

3) and (3) mould pressing treatment: placing the uniformly mixed material obtained in the step 2) into a mould pressing tool, controlling the pressure to be 30MPa, maintaining the pressure at 40 ℃ for 1.5h, and demoulding to obtain a mould;

4) pre-drying treatment: placing the model in the step 3) in an electric heating blast drying oven, drying for 2h at 40 ℃, and then heating to 100 ℃ and drying for 3h to obtain a mould pressing ceramic blank;

5) high-temperature treatment for the first time: placing the molded ceramic blank in the step 4) in a high-temperature furnace, controlling the heating rate to be 2 ℃/min, heating to 650 ℃, preserving heat for 3h, and then cooling to room temperature;

6) gel impregnation treatment: placing the embryo body obtained in the step 5) in a medium with a solid content of 25%, a particle size of 15-20 nm, a pH value of 4 at 20 ℃ and a dynamic viscosity of 5 multiplied by 10 at 25 DEG^-3Soaking in Pa & S silica sol for 8 h; wherein the temperature of the silica sol is 90 ℃;

7) and (3) second high-temperature treatment: and (3) placing the blank treated in the step 6) into a high-temperature furnace, firstly controlling the heating rate to be 2 ℃/min, heating to 110 ℃, preserving heat for 3h, then controlling the heating rate to be 5 ℃/min, heating to 1400 ℃, preserving heat for 3h, cooling to room temperature, and taking out to obtain the silicon oxide short fiber mould pressing ceramic antenna window composite material.

The material prepared by the embodiment has good surface quality, and does not have the conditions of pits, slag falling and the like. The properties of the test specimens were tested and the results are shown in Table 3.

Table 3 composite Properties List

Example 4

The embodiment discloses a silicon oxide short fiber die-pressed ceramic antenna window composite material, which comprises the following preparation steps:

1) preparing a silica gel: taking the solid content of 40 percent, the particle diameter of 10-15 nm, the pH value of 4 at 20 ℃ and the dynamic viscosity of 10 multiplied by 10 at 25 DEG C^-3Heating the Pa.S silica sol in a water bath at 90 ℃ for 20h to convert the silica sol into silica gel;

2) material mixing: smashing the silica gel prepared in the step 1) to form uniform particles with the particle size of about 1.5mm, uniformly mixing the particles with silicon oxide short fibers with the length of 4mm according to the mass ratio of 1:1.3, placing the mixture in a vacuum bag, and maintaining the pressure for 30min in a negative pressure environment of-80 kPa;

3) and (3) mould pressing treatment: placing the uniformly mixed material obtained in the step 2) into a mould pressing tool, controlling the pressure to be 40MPa, maintaining the pressure at 50 ℃ for 1.5h, and demoulding to obtain a mould;

4) pre-drying treatment: placing the model in the step 3) in an electric heating blast drying oven, drying for 2h at 40 ℃, and then heating to 100 ℃ and drying for 3h to obtain a mould pressing ceramic blank;

5) high-temperature treatment for the first time: placing the molded ceramic blank in the step 4) in a high-temperature furnace, controlling the heating rate to be 2 ℃/min, heating to 650 ℃, preserving heat for 3h, and then cooling to room temperature;

6) gel impregnation treatment: placing the embryo body obtained in the step 5) in a reactor with the solid content of 23%, the particle size of 10-15 nm, the pH value of 3 at 20 ℃ and the dynamic viscosity of 10 multiplied by 10 at 25 DEG C^-3Soaking in Pa & S silica sol for 6 h; wherein the temperature of the silica sol is 90 ℃;

7) and (3) second high-temperature treatment: and (3) placing the blank treated in the step 6) into a high-temperature furnace, firstly controlling the heating rate to be 2 ℃/min, heating to 110 ℃, preserving heat for 3h, then controlling the heating rate to be 5 ℃/min, heating to 1400 ℃, preserving heat for 3h, cooling to room temperature, and taking out to obtain the silicon oxide short fiber mould pressing ceramic antenna window composite material.

The material prepared by the embodiment has good surface quality, and does not have the conditions of pits, slag falling and the like. The properties of the test specimens were tested and the results are shown in Table 4.

Table 4 composite Properties List

Example 5

The difference from example 4 is that in step 2), the pressure is maintained for 30min under a negative pressure environment of-70 kPa, and the rest is the same.

Example 6

Different from the embodiment 4, the mass ratio in the step 2) is 1: 1.35.

Example 7

Different from the embodiment 4, the mass ratio in the step 2) is 1: 1.37.

Example 8

Different from the embodiment 4, the mass ratio in the step 2) is 1: 1.4.

Example 9

Different from the embodiment 4, in the step 4), the mold in the step 3) is placed in an electric heating air blast drying oven, dried for 2 hours at the temperature of 45 ℃, and then dried for 3 hours after being heated to the temperature of 110 ℃, so that the molded ceramic blank is obtained.

Example 10

Different from the embodiment 4, in the step 4), the mold in the step 3) is placed in an electric heating air blast drying oven, dried for 2 hours at the temperature of 55 ℃, and then dried for 3 hours after being heated to the temperature of 120 ℃, so that the mold-pressed ceramic blank is obtained.

Example 11

Different from the embodiment 4, in the step 5), the molded ceramic blank in the step 4) is placed in a high-temperature furnace, the temperature rise speed is controlled to be 3.5 ℃/min, the temperature is raised to 700 ℃, the temperature is kept for 3h, and then the temperature is reduced to the room temperature.

Example 12

Different from the embodiment 4, in the step 5), the molded ceramic blank in the step 4) is placed in a high-temperature furnace, the temperature rise speed is controlled to be 5 ℃/min, the temperature is raised to 800 ℃, and the temperature is kept for 3h and then is reduced to the room temperature.

Example 13

Different from the embodiment 4, in the step 7), the blank processed in the step 6) is placed in a high temperature furnace, the temperature rise speed is controlled to be 3 ℃/min, the temperature is raised to 130 ℃ and is kept for 3h, then the temperature rise speed is controlled to be 5 ℃/min, the temperature is raised to 1400 ℃, the temperature is kept for 3h, and the blank is taken out after being cooled to the room temperature, so that the silicon oxide short fiber die-pressed ceramic antenna window composite material is prepared.

As a result, the product meeting the requirements can be prepared by meeting the process conditions designed by the invention.

Comparative example 1

Compared with the embodiment 1, the vacuum bag treatment in the negative pressure environment of the step 2) is not carried out, and the rest is the same.

Comparative example 2

Step 6) is omitted as compared with example 1), and the others are the same.

Compared with a comparative product, the product prepared by the preparation method has the advantages of relatively higher density, fewer surface micropores and pits and better heat insulation performance.

The above examples are merely preferred examples and are not intended to limit the embodiments of the present invention. In addition to the above embodiments, the present invention has other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.