High-performance silicon carbide ceramic fiber membrane and preparation method thereof

Abstract

The invention belongs to the technical field of fiber preparation, and relates to a high-performance silicon carbide ceramic fiber membrane and a preparation method thereof. The silicon carbide ceramic fiber membrane is prepared from phenylboronic acid or a derivative thereof and an organosilicon polymer as raw materials through the steps of spinning, electron beam irradiation non-melting, sintering and high-temperature sintering. The preparation method of the silicon carbide ceramic fiber membrane provided by the invention has the characteristics of simplicity and high efficiency, and the prepared ceramic fiber membrane has excellent wave absorption and high temperature resistance, and has important application value in the fields of aviation, aerospace, national defense, energy and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber preparation and relates to a high-performance silicon carbide ceramic fiber membrane and a preparation method thereof. Background Art

[0002] Ceramic fiber has the characteristics of high temperature resistance, corrosion resistance, oxidation resistance, good insulation and heat insulation, and has broad application prospects in aerospace, high temperature filtration, thermal insulation and other fields. Traditional aluminum silicate ceramic fibers will produce fine dust particles during use. These particles are easy to induce respiratory inflammation and even cancer. This problem seriously limits its application in some fields with high requirements for the environment and human health. In order to replace aluminum silicate ceramic fibers, researchers have developed calcium magnesium silicon series ceramic fibers. However, this fiber still has many problems: the melting temperature of its raw materials is high, which requires higher energy input during the preparation process, increases production costs and process difficulty; the fiber-forming process is difficult to operate, resulting in low production efficiency and difficult to control product quality; and the performance of its fiber needs to be improved. For example, in terms of mechanical strength and flexibility, it cannot meet the needs of some complex application scenarios, and it also performs poorly in thermal insulation structures that require frequent bending or withstand large external forces.

[0003] In recent years, researchers have used electrospinning technology to prepare flexible and high-temperature resistant SiO2 ceramic nanofiber membranes. It has low thermal conductivity, good mechanical strength and thermal stability, and can preserve its fiber morphology and structure at 800-1200°C. It is suitable for some medium and high temperature insulation and filtration applications. Its use at higher temperatures is limited and cannot meet the needs of some extreme high temperature environments (such as hot end components of aircraft engines, ultra-high temperature industrial reactors, etc.). In recent years, researchers have used precursor conversion method and electrospinning technology to prepare flexible and high temperature resistant silicon carbide fiber membrane materials. This material has good flexibility and excellent thermal stability. The precursor conversion method has good designability and can prepare silicon carbide ceramic fiber materials with various functions. However, its high temperature resistance is limited by the oxygen content. The higher the oxygen content, the worse the high temperature resistance. Strict control of oxygen content is the key to improving its high temperature resistance. In addition, the process of the precursor conversion method is relatively complicated, the preparation efficiency is low, and the production cost is high, which limits its wide application in some fields. Especially for the infusible process, the currently commonly used air oxidation method and radiation cross-linking method have the problems of low efficiency, long time consumption and high energy consumption. In order to avoid the melting of the fibers, the conventional air oxidation method must be carried out at an extremely slow heating rate, and the radiation cross-linking method must also be carried out at a lower radiation dose rate. As a result, the production efficiency of silicon carbide ceramic fibers is very low and the production cost is very high, which cannot meet the application requirements of some cost-sensitive fields. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide a high-performance silicon carbide ceramic fiber membrane and a preparation method thereof, so as to overcome the shortcomings of the prior art.

[0005] One object of the present invention is to provide a high-performance silicon carbide ceramic fiber membrane, which is prepared from boron-containing compounds and organosilicon polymers through the steps of spinning, electron beam irradiation, infusibility, firing, and high-temperature sintering;

[0006] The boron-containing compound is phenylboric acid or its derivatives, and the molecular structure of the phenylboric acid derivative is as follows:

[0007]

[0008] In the formula, R1 and R2 are independently selected from -(CH2) n CH2-, wherein n, x, and y are independently integers of 0 to 10.

[0009] Preferably, in the molecular structural formula of the phenylboronic acid derivative, n, x, and y are independently integers of 0-5.

[0010] Preferably, the boron-containing compound is one or more of phenylboric acid, phenylboric acid pinacol ester, and phenylboric acid 1,3-propylene glycol ester.

[0011] Preferably, the organosilicon polymer is polycarbosilane doped with metal elements, also called polymetallic carbosilane (PMCS), and the metal element (M) is one or more of aluminum, zirconium, titanium, yttrium and the like.

[0012] Preferably, the organosilicon polymer is one or more of polyaluminum carbosilane, polyzirconium carbosilane, polytitanium carbosilane, polyyttrium carbosilane and the like.

[0013] Preferably, the metal element doping amount in the metal element doped polycarbosilane is 0.1 to 10 wt %, more preferably 0.5 to 5 wt %.

[0014] Preferably, the content of the boron-containing compound relative to the organosilicon polymer is 0.05 to 25 wt %, more preferably 0.1 to 20 wt %.

[0015] Preferably, the spinning is electrospinning or melt-blowing spinning.

[0016] During electrospinning, the boron-containing compound and the organosilicon polymer are dissolved in an organic solvent to form a spinning solution, and then the spinning solution is placed in a spinning device for electrospinning to obtain a fibril membrane. The above-mentioned organic solvent is any solvent that can dissolve the organosilicon polymer modified by the boron-containing compound, including one or more of toluene, xylene, tetrahydrofuran, acetone, n-hexane, and chloroform. The process parameters of electrospinning can be listed as follows: the electrospinning voltage is 10 to 25 kV, the distance between the stainless steel needle and the fiber collector is 5 to 25 cm, and the feeding rate of the spinning solution is 0.01 to 0.1 mL / min.

[0017] During melt-blowing, the mixture of the boron-containing compound and the organosilicon polymer is heated to obtain a melt, which is then spun and collected to obtain a fibril membrane. The mixture of the boron-containing compound and the organosilicon polymer can be obtained by physically mixing the boron-containing compound and the organosilicon polymer; or it can be obtained by dissolving the boron-containing compound and the organosilicon polymer in an organic solvent, mixing them evenly, and then removing the organic solvent.

[0018] Preferably, the fiber diameter of the fibril membrane obtained by spinning is 1 to 10 μm, preferably 3 to 5 μm.

[0019] The electron beam irradiation infusibility of the present invention is carried out by electron beam irradiation in an oxygen-containing atmosphere. In order to avoid fiber fusion of the organic fiber membrane during high-temperature treatment, electron beam irradiation is used to quickly infusible the organic fiber membrane in an oxygen-containing atmosphere, so that sufficient cross-linking reaction occurs between the boron-containing compound and the organic silicon polymer molecules. The electron beam energy is 1 to 5 MeV, and the beam current is 1 to 50 mA.

[0020] Preferably, the irradiation dose for the electron beam irradiation to not cause melting is 1 to 10 MGy, preferably 2 to 5 MGy.

[0021] Preferably, the electron beam irradiation time for not melting is 0.1 to 5 hours, preferably 20 to 120 minutes.

[0022] Preferably, the oxygen-containing atmosphere is composed of oxygen and inert gas, wherein the content of oxygen is 0.5 to 10 v / v%, preferably 1 to 8 v / v%.

[0023] Preferably, the sintering is carried out in an inert atmosphere, the treatment temperature is 1000-1300°C, and the treatment time is 10-60 minutes. The inert atmosphere herein includes one of nitrogen, argon, and helium. More preferably, the sintering is carried out in a nitrogen atmosphere.

[0024] Preferably, the high temperature sintering is performed in an inert atmosphere, the treatment temperature is 1500-2000° C., and the treatment time is 10-60 min. More preferably, the sintering is performed in an argon atmosphere.

[0025] Preferably, the high-performance silicon carbide ceramic fiber membrane is prepared from boron-containing compounds and organosilicon polymers through the steps of spinning, electron beam irradiation, infusibility, annealing, firing, and high-temperature sintering;

[0026] The annealing temperature is 200-300° C., and the annealing time is 10-60 minutes.

[0027] Preferably, the high-performance silicon carbide ceramic fiber membrane has an oxygen content of ≤1.5wt% and a minimum reflection loss of ≤-35dB when the thickness is 1.5 to 3.0 mm.

[0028] Preferably, the high-performance silicon carbide ceramic fiber membrane has an oxygen content of ≤1.0 wt %, and has a minimum reflection loss of ≤-40 dB when the thickness is 1.5 to 3.0 mm.

[0029] The second object of the present invention is to provide a method for preparing a high-performance silicon carbide ceramic fiber membrane, comprising the following steps:

[0030] Spinning raw materials to obtain raw fibers, wherein the raw materials include boron-containing compounds and organosilicon polymers;

[0031] The fibrils are subjected to electron beam irradiation in an oxygen-containing atmosphere to infusibility treatment;

[0032] Then it is fired and sintered at high temperature;

[0033] The boron-containing compound is phenylboric acid or its derivatives, and the molecular structure of the phenylboric acid derivative is as follows:

[0034]

[0035] In the formula, R1 and R2 are independently selected from -(CH2) n CH2-, wherein n, x, and y are independently integers of 0 to 10.

[0036] Preferably, the step further comprises: after the electron beam irradiation infusibility treatment, an annealing treatment is performed, the annealing temperature is 200 to 300° C., and the annealing time is 10 to 60 minutes.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The boron-containing compound and the organosilicon polymer of the present invention are used as raw materials for preparing silicon carbide fibers, wherein the boron-containing compound is phenylboric acid or its derivatives, thereby realizing the controllable introduction of boron into the silicon carbide fibers, with less loss of boron source and uniform distribution in the fibers, which significantly promotes high-temperature sintering densification; and it has been proven that the raw materials can be subjected to infusibility treatment by electron beam irradiation, and a higher irradiation dose rate can be used, and the infusibility treatment time is greatly shortened, thereby overcoming the shortcomings of the traditional air oxidation method and the irradiation cross-linking method.

[0039] 2. The present invention uses boron-containing compounds and organosilicon polymers as raw materials for preparing silicon carbide fibers, and combines them with electron beam irradiation for infusibility treatment, which significantly improves the flexibility of the silicon carbide ceramic fiber membrane and improves the fiber's wave absorbing performance.

[0040] 3. When the boron-containing compound is phenylboronic acid pinacol ester or phenylboronic acid 1,3-propylene glycol ester, the prepared silicon carbide ceramic fiber membrane has more excellent wave absorbing performance.

[0041] 4. The present invention further performs annealing after the infusible treatment, which is beneficial to improving the ceramic yield of the infusible fiber membrane.

[0042] 5. The silicon carbide ceramic fiber membrane prepared by the present invention has the properties of low oxygen content, good flexibility, high temperature resistance, oxidation resistance and wave absorption, and has important application value in the fields of aviation, aerospace, national defense, energy, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is an optical photograph of the silicon carbide ceramic fiber membrane prepared in Example 1 of the present invention;

[0044] Figure 2 is a SEM photograph of the silicon carbide ceramic fiber membrane prepared in Example 1 of the present invention;

[0045] Figure 3 is a reflection loss value curve of the silicon carbide ceramic fiber membrane prepared in Example 1 of the present invention; DETAILED DESCRIPTION

[0046] The technical scheme of the present invention is further described below by specific examples and accompanying drawings. It should be understood that the specific examples described herein are only used to help understand the present invention and are not intended for specific limitations of the present invention. The accompanying drawings used herein are only for better illustrating the disclosure of the present invention and do not have a limiting effect on the scope of protection. If not otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0047] In the following examples and comparative examples:

[0048] The weight average molecular weight of polyaluminocarbosilane is about 3300 g / mol, and the aluminum content is about 0.6 wt %;

[0049] The weight average molecular weight of the polyzirconium carbosilane is about 3000 g / mol, and the zirconium content is about 1 wt %;

[0050] The weight average molecular weight of the polytitanium carbosilane is about 3000 g / mol, and the titanium content is about 1 wt %;

[0051] The weight average molecular weight of polyyttrium carbosilane is about 3000 g / mol, and the yttrium content is about 1 wt%;

[0052] The electron beam irradiation oxidation process uses a 2MeV electron accelerator with a beam current of 2 to 20 mA.

[0053] Structural characterization and performance testing:

[0054] The oxygen content of silicon carbide fiber membrane was tested by oxygen and nitrogen analyzer (EMGA-620W, LECO, USA). The boron content in silicon carbide fiber membrane was tested by inductively coupled plasma atomic emission spectrometer (ICP-OES) (SPECTRO ACROS, Germany). The micromorphology of silicon carbide fiber was characterized by scanning electron microscope (SEM, FEI, USA). The high temperature oxidation ablation resistance of silicon carbide fiber membrane was evaluated at about 1100°C using butane blowtorch flame. In argon atmosphere, the ceramic yield of infusible fiber membrane was characterized by thermogravimetric analyzer at a heating rate of 10°C / min. The silicon carbide fiber membrane was ground into powder, mixed with paraffin in a ratio of 7:3 (w / w), and pressed into a composite ring with an inner diameter of 3mm and an outer diameter of 7mm. Then, the complex dielectric constant (ε) of the composite ring was measured in the frequency range of 2-18GHz using a vector network analyzer (E5063A) from Keysight Technologies, USA. r =ε′-jε″) and magnetic permeability (μ r =μ′-jμ″), based on the transmission line theory and the metal backplane model, the reflection loss (RL) of the SiC fiber is calculated by formulas (1) to (3) to evaluate its microwave absorption performance.

[0055]

[0056]

[0057] Example 1

[0058] The silicon carbide ceramic fiber membrane of this embodiment is prepared by the following method:

[0059] Phenylboric acid and polyaluminocarbosilane (1:10, w / w) were dissolved in a mixed solvent of xylene and acetone (3:1, w / w), stirred to prepare a uniform solution with a concentration of about 60wt%, and after standing to degas, a spinning solution was obtained, and an organic fiber membrane was prepared by electrospinning. The electrospinning voltage was 12kV, the distance between the stainless steel needle and the fiber collector was 15cm, the feeding rate of the spinning solution was set to 0.04mL / min, and the fiber was collected on aluminum foil. Electron beam irradiation was used to make it infusible, the irradiation dose was 2.2MGy, the irradiation time was 22min, and the atmosphere was argon and oxygen (95:5, v / v). The infusible fiber membrane was sintered at 1200℃ nitrogen atmosphere for 30min, and then high-temperature sintering was carried out at 1900℃ argon atmosphere for 30min to obtain a silicon carbide ceramic fiber membrane.

[0060] Figure 1 This is an optical photograph of the silicon carbide ceramic fiber membrane prepared in Example 1. It can be seen that a membrane-like product is prepared. Figure 2 This is a SEM photo of the silicon carbide ceramic fiber membrane prepared in Example 1. It can be seen that the fibers are randomly arranged and no welding occurs, indicating that the spinning solution has good spinnability. The electron beam irradiation infusibility treatment allows sufficient cross-linking reaction between the boron-containing compound and the organic silicon polymer molecules. The ceramic yield of the infusible fiber membrane is 68%. The subsequent high-temperature treatment did not cause fiber melting. The fiber diameter is approximately between 3 and 5 μm.

[0061] The silicon carbide ceramic fiber membrane has an oxygen content of 0.21% and a boron content of 0.17%. It has good flexibility, high temperature resistance and ablation resistance. It remains intact and maintains good flexibility after being ablated for 40 seconds in air with a butane torch flame (about 1100°C). The ceramic fiber membrane also has good wave absorption properties, such as Figure 3 As shown, a minimum reflection loss of -41.8 dB was achieved at 12 GHz with a thickness of 1.5 mm.

[0062] Example 2

[0063] The difference between Example 2 and Example 1 is that Example 2 uses phenylboronic acid pinacol ester instead of phenylboric acid, and the rest is the same as Example 1 to prepare a silicon carbide ceramic fiber membrane.

[0064] The ceramic yield of the infusible fiber membrane is 70%. The oxygen content of the silicon carbide ceramic fiber membrane is 0.21%, the boron content is 0.18%, and it has good flexibility, high temperature resistance and ablation resistance. It is ablated in the air with a butane torch flame (about 1100°C) for 40s and remains intact and maintains good flexibility. The ceramic fiber membrane has good wave absorption performance and achieves a minimum reflection loss of -43.5dB at a thickness of 2.0 mm and 10GHz.

[0065] Example 3

[0066] The difference between Example 3 and Example 1 is that Example 3 uses 1,3-propylene glycol phenylborate to replace phenylboric acid, and the rest is the same as Example 1 to prepare a silicon carbide ceramic fiber membrane.

[0067] The ceramic yield of the infusible fiber membrane is 71%. The oxygen content of the silicon carbide ceramic fiber membrane is 0.20%, the boron content is 0.18%, and it has good flexibility, high temperature resistance and ablation resistance. It is ablated in the air with a butane torch flame (about 1100°C) for 40s and remains intact and maintains good flexibility. The ceramic fiber membrane has good wave absorption performance and achieves a minimum reflection loss of -44.2dB at a thickness of 1.5 mm and 12GHz.

[0068] Example 4

[0069] Phenylboric acid, polyaluminum carbosilane and polyzirconium carbosilane (10:50:50, w / w) were dissolved in xylene, and then the xylene was evaporated under vacuum to obtain a mixture of phenylboric acid, polyaluminum carbosilane and polyzirconium carbosilane, and an organic fiber membrane was prepared by melt-blowing. The specific process of melt-blown spinning is as follows: add a mixture of phenylboric acid, polyaluminum carbosilane and polyzirconium carbosilane into a melting kettle, vacuumize and replace with nitrogen three times, remove the air in the kettle, quickly heat to 350°C, keep warm for 1 hour, let stand to remove bubbles, and then reduce the temperature of the melting kettle to 300°C; heat the spinning phase to the same temperature and maintain it, and when the temperature inside and outside the spinneret of the spinning assembly is basically the same, increase the pressure in the kettle to 0.35MPa and maintain it, turn on the booster pump and metering pump, and start spinning; with the help of high-speed hot air flow, the newly extruded melt is quickly stretched and solidified; the melt stream is stretched under the action of high-temperature hot air flow, and the hot air flow is mixed with the surrounding air to cool the fiber and finally form it. It is treated by electron beam irradiation to make it infusible, with an irradiation dose of 3.0MGy, an irradiation time of 30min, and an atmosphere of argon and oxygen (95:4, v / v). The infusible fiber was sintered at 1150°C in a nitrogen atmosphere for 40 minutes, and then subjected to a high-temperature sintering treatment at 1500°C in an argon atmosphere for 45 minutes to obtain a silicon carbide ceramic fiber membrane.

[0070] The ceramic fiber membrane has an oxygen content of 1.30% and a boron content of 0.16%. It has good flexibility, high temperature resistance and ablation resistance. It remains intact and maintains good flexibility after being ablated for 40 seconds in air with a butane blowtorch flame (about 1100°C).

[0071] Example 5

[0072] Phenylboric acid, polyaluminum carbosilane and polytitanium carbosilane (10:50:50, w / w) were dissolved in xylene, and then the xylene was evaporated under vacuum to obtain a mixture of phenylboric acid, polyaluminum carbosilane and polytitanium carbosilane, and an organic fiber membrane was prepared by melt-blowing. The specific process of melt-blown spinning is as follows: add a mixture of phenylboric acid, polyaluminum carbosilane and polytitanium carbosilane into a melting kettle, vacuumize and replace with nitrogen three times, remove the air in the kettle, quickly heat to 350°C, keep warm for 1 hour, let stand to remove bubbles, and then reduce the temperature of the melting kettle to 300°C; heat the spinning phase to the same temperature and maintain it, and when the temperature inside and outside the spinneret of the spinning assembly is basically the same, increase the pressure in the kettle to 0.35MPa and maintain it, turn on the booster pump and metering pump, and start spinning; with the help of high-speed hot air flow, the newly extruded melt is quickly stretched and solidified; the melt stream is stretched under the action of high-temperature hot air flow, and the hot air flow is mixed with the surrounding air to cool the fiber and finally form it. It is treated by electron beam irradiation to make it infusible, with an irradiation dose of 5.0MGy, an irradiation time of 50min, and an atmosphere of argon and oxygen (95:6, v / v). The infusible fiber was sintered at 1250°C in a nitrogen atmosphere for 25 minutes, and then subjected to a high-temperature sintering treatment at 1700°C in an argon atmosphere for 25 minutes to obtain a silicon carbide ceramic fiber membrane.

[0073] The ceramic fiber membrane has an oxygen content of 0.60% and a boron content of 0.10%. It has good flexibility, high temperature resistance and ablation resistance. It remains intact and maintains good flexibility after being ablated for 40 seconds in air with a butane blowtorch flame (about 1100°C).

[0074] Example 6

[0075] The silicon carbide ceramic fiber membrane of this embodiment is prepared by the following method:

[0076] Phenylboric acid and polyyttrium carbosilane (1:8, w / w) were dissolved in a mixed solvent of xylene and acetone (3:1, w / w), stirred to prepare a uniform solution with a concentration of about 65wt%, and after standing to degas, a spinning solution was obtained, and an organic fiber membrane was prepared by electrospinning. The electrospinning voltage was 14kV, the distance between the stainless steel needle and the fiber collector was 16cm, the feeding rate of the spinning solution was set to 0.05mL / min, and the fiber was collected on aluminum foil. Electron beam irradiation was used to make it infusible, the irradiation dose was 3.2MGy, the irradiation time was 25min, and the atmosphere was argon and oxygen (95:5, v / v). The infusible fiber membrane was sintered at 1200℃ nitrogen atmosphere for 35min, and then high-temperature sintering was carried out at 1800℃ argon atmosphere for 35min to obtain a silicon carbide ceramic fiber membrane.

[0077] The silicon carbide ceramic fiber membrane has an oxygen content of 0.5% and a boron content of 0.13%. It has good flexibility, high temperature resistance and ablation resistance. It remains intact and maintains good flexibility after being ablated in air with a butane torch flame (about 1100°C) for 40 seconds. The ceramic fiber membrane also has good wave absorption performance, achieving a minimum reflection loss of -40.5dB at 10GHz with a thickness of 1.5 mm.

[0078] Example 7

[0079] The difference between Example 7 and Example 1 is that after the infusible treatment, Example 7 further adopts annealing treatment, and the rest is the same as Example 1, and the specific steps are:

[0080] Phenylboric acid and polyaluminocarbosilane (1:10, w / w) were dissolved in a mixed solvent of xylene and acetone (3:1, w / w), stirred to prepare a uniform solution with a concentration of about 60wt%, and after standing to degas, a spinning solution was obtained, and an organic fiber membrane was prepared by electrospinning. The electrospinning voltage was 12kV, the distance between the stainless steel needle and the fiber collector was 15cm, the feeding rate of the spinning solution was set to 0.04mL / min, and the fiber was collected on aluminum foil. Electron beam irradiation was used to make it infusible, the irradiation dose was 2.2MGy, the irradiation time was 22min, and the atmosphere was argon and oxygen (95:5, v / v). The infusible fiber membrane was annealed at 250℃ for 30min. After cooling to room temperature, the temperature was raised to 1200℃ again and the fiber was sintered for 30min in a nitrogen atmosphere, and then the silicon carbide ceramic fiber membrane was prepared by high-temperature sintering at 1900℃ in an argon atmosphere for 30min.

[0081] The ceramic yield of the infusible fiber membrane is 82%. The oxygen content of the silicon carbide ceramic fiber membrane is 0.20%, the boron content is 0.17%, and it has good flexibility, high temperature resistance and ablation resistance. It is ablated in the air with a butane torch flame (about 1100°C) for 40s and remains intact and maintains good flexibility. The ceramic fiber membrane has good wave absorption performance and achieves a minimum reflection loss of -42.2dB at a thickness of 1.5 mm and 11GHz.

[0082] Example 8

[0083] The difference between Example 8 and Example 2 is that after the infusibility treatment, Example 8 further adopts annealing treatment, the annealing temperature is 240° C., the annealing time is 40 min, and the rest is the same as Example 1.

[0084] The ceramic yield of the infusible fiber membrane is 81%. The oxygen content of the silicon carbide ceramic fiber membrane is 0.19%, the boron content is 0.17%, and it has good flexibility, high temperature resistance and ablation resistance. It is still intact and maintains good flexibility after being ablated for 40 seconds with a butane torch flame (about 1100°C) in air. The ceramic fiber membrane has good wave absorption performance and achieves a minimum reflection loss of -43.9dB at a thickness of 2.0 mm and 11GHz.

[0085] Example 9

[0086] The difference between Example 9 and Example 3 is that after the infusibility treatment, Example 9 further adopts annealing treatment, the annealing temperature is 260° C., the annealing time is 35 min, and the rest is the same as Example 1.

[0087] The ceramic yield of the infusible fiber membrane is 84%. The oxygen content of the silicon carbide ceramic fiber membrane is 0.19%, the boron content is 0.18%, and it has good flexibility, high temperature resistance and ablation resistance. It is still intact and maintains good flexibility after being ablated in the air with a butane torch flame (about 1100°C) for 40s. The ceramic fiber membrane has good wave absorption performance and achieves a minimum reflection loss of -45.1dB at a thickness of 2.0 mm and 13GHz.

[0088] Comparative Example 1

[0089] The difference between the preparation method of the silicon carbide ceramic fiber membrane of Comparative Example 1 and that of Example 1 is that no phenylboric acid is added in Comparative Example 1, and the conventional air oxidation method is used for infusibility treatment in Comparative Example 1, and the rest is the same as that of Example 1. The specific steps are:

[0090] Polyaluminocarbosilane was dissolved in a mixed solvent of xylene and acetone (3:1, w / w), stirred to prepare a uniform solution with a concentration of about 60wt%, and after standing for degassing, a spinning solution was obtained, and an organic fiber membrane was prepared by electrospinning. The electrospinning voltage was 12kV, the distance between the stainless steel needle and the fiber collector was 15cm, the feeding rate of the spinning solution was set to 0.04mL / min, and the fibers were collected on aluminum foil. The fiber membrane was infusible by air oxidation, with a heating rate of 10℃ / h and a constant temperature of 205℃ for 2h. The infusible fiber membrane was sintered for 30min in a nitrogen atmosphere at 1200℃, and then sintered at high temperature for 30min in an argon atmosphere at 1900℃ to obtain a silicon carbide ceramic fiber membrane.

[0091] The ceramic yield of the infusible fiber membrane is 77%. The ceramic fiber membrane has poor flexibility and is easily broken. The minimum reflection loss of the ceramic fiber at a thickness of 5.5 mm and 15 GHz is -18 dB.

[0092] Comparative Example 2

[0093] The difference between the preparation method of the silicon carbide ceramic fiber membrane of Comparative Example 2 and that of Example 1 is that the conventional air oxidation method is used for infusibility treatment in Comparative Example 2, and the rest is the same as that of Example 1. The specific steps are:

[0094] Phenylboric acid and polyaluminocarbosilane (1:10, w / w) were dissolved in a mixed solvent of xylene and acetone (3:1, w / w), stirred to prepare a uniform solution with a concentration of about 60wt%, and after standing to degas, a spinning solution was obtained, and an organic fiber membrane was prepared by electrospinning. The electrospinning voltage was 12kV, the distance between the stainless steel needle and the fiber collector was 15cm, the feeding rate of the spinning solution was set to 0.04mL / min, and the fibers were collected on aluminum foil. The fiber membrane was treated with infusibility by air oxidation, with a heating rate of 10℃ / h and a constant temperature of 205℃ for 2h. The infusible fiber membrane was sintered for 30min in a nitrogen atmosphere at 1200℃, and then sintered at high temperature for 30min in an argon atmosphere at 1900℃ to obtain a silicon carbide ceramic fiber membrane.

[0095] The ceramic yield of the infusible fiber membrane is 80%. The oxygen content of the ceramic fiber membrane is 0.50%, and the boron content is 0.15%. It has good flexibility. The minimum reflection loss of the ceramic fiber at a thickness of 3 mm and 7 GHz is -34 dB.

[0096] Comparative Example 3

[0097] The difference between the preparation method of the silicon carbide ceramic fiber membrane of Comparative Example 3 and that of Example 1 is that phenylboric acid is not added in Comparative Example 3, and the rest is the same as that of Example 1. The specific steps are:

[0098] Polyaluminocarbosilane was dissolved in a mixed solvent of xylene and acetone (3:1, w / w), stirred to prepare a uniform solution with a concentration of about 60wt%, and after standing to degas, a spinning solution was obtained, and an organic fiber membrane was prepared by electrospinning. The electrospinning voltage was 12kV, the distance between the stainless steel needle and the fiber collector was 15cm, the feeding rate of the spinning solution was set to 0.04mL / min, and the fiber was collected on aluminum foil. It was treated by electron beam irradiation for infusibility, the irradiation dose was 2.2MGy, the irradiation time was 22min, and the atmosphere was argon and oxygen (95:5, v / v). The infusible fiber membrane was sintered at 1200℃ nitrogen atmosphere for 30min, and then high-temperature sintered at 1900℃ argon atmosphere for 30min to obtain a silicon carbide ceramic fiber membrane.

[0099] The ceramic yield of the infusible fiber membrane is 70%. The oxygen content of the ceramic fiber membrane is 0.29%, and the membrane has good flexibility. The minimum reflection loss of the ceramic fiber at a thickness of 1.5 mm and 7 GHz is -28 dB.

[0100] Compared with Comparative Examples 1-3, the silicon carbide ceramic fiber membrane prepared in Example 1-9 exhibits more excellent wave absorption performance, indicating that the use of boron-containing compounds and organosilicon polymers as raw materials and the infusibility treatment combined with electron beam irradiation is beneficial to improving the wave absorption performance of the fiber membrane. Boron-containing compounds of different structures will affect the performance of the fiber membrane. It can be seen from the comparison of Examples 1-3 that when the boron-containing compounds are selected from phenylboronic acid pinacol ester and phenylboronic acid 1,3-propylene glycol ester, they have better wave absorption performance than phenylboric acid. By comparing Example 1 with Comparative Examples 1-3, it is found that the ceramic yield of Example 1 without annealing treatment is reduced, and by annealing after the infusibility treatment, it is beneficial to improve the ceramic yield, as shown in the experimental data of Examples 7-9 and Examples 1-3.

[0101] In the above embodiments, the silicon carbide ceramic fiber membranes prepared in embodiments 7-9 not only have excellent wave absorbing properties, but also have a high ceramic yield of the infusible fiber membrane.

[0102] The various aspects, embodiments, and features of the present invention should be considered to be illustrative in all aspects and not limiting of the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0103] In the preparation method of the present invention, the order of each step is not limited to the order listed. For those skilled in the art, without creative work, the order of each step is also within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0104] Finally, it should be noted that the specific embodiments described herein are merely examples of the present invention, and are not intended to limit the implementation methods of the present invention. A person skilled in the art of the present invention may make various modifications or supplements to the specific embodiments described, or replace them in a similar manner. It is not necessary and impossible to provide all examples of all implementation methods here. However, these obvious changes or modifications derived from the essential spirit of the present invention still fall within the scope of protection of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A high performance silicon carbide ceramic fiber membrane, characterized in that: It is made of boron-containing compounds and organosilicon polymers as raw materials, and is prepared through the steps of spinning, electron beam irradiation, infusibility, firing, and high-temperature sintering; The boron-containing compound is phenylboric acid or its derivatives, and the molecular structure of the phenylboric acid derivative is as follows: In the formula, R1 and R2 are independently selected from -(CH2) n CH2-, wherein n, x, and y are independently integers of 0 to 10.

2. A high performance silicon carbide ceramic fiber membrane according to claim 1, characterized in that: The boron-containing compound is one or more of phenylboric acid, phenylboric acid pinacol ester, and phenylboric acid 1,3-propylene glycol ester.

3. A high performance silicon carbide ceramic fiber membrane according to claim 1, characterized in that: The organosilicon polymer is polycarbosilane doped with metal elements, wherein the metal element doping amount in the polycarbosilane is 0.1 to 10 wt %; And / or, the organosilicon polymer is one or more of polyaluminum carbosilane, polyzirconium carbosilane, polytitanium carbosilane, and polyyttrium carbosilane; And / or, the content of the boron-containing compound relative to the organosilicon polymer is 0.05 to 25 wt %.

4. A high performance silicon carbide ceramic fiber membrane according to claim 1, characterized in that: The spinning is electrostatic spinning or melt-blown spinning; The fiber diameter of the fibril membrane obtained by spinning is 1 to 10 μm.

5. The high performance silicon carbide ceramic fiber membrane according to claim 1, characterized in that: Electron beam irradiation infusion is carried out by electron beam irradiation in an oxygen-containing atmosphere; The irradiation dose for the electron beam irradiation to not melt is 1 to 10 MGy, and the time for the electron beam irradiation to not melt is 0.1 to 5 hours; The oxygen-containing atmosphere is composed of oxygen and inert gas, wherein the content of oxygen is 0.5-10 v / v%.

6. A high performance silicon carbide ceramic fiber membrane according to claim 1, characterized in that: The sintering is carried out in an inert atmosphere at a temperature of 1000 to 1300° C. for a time of 10 to 60 minutes; And / or, the high temperature sintering is carried out in an inert atmosphere, the processing temperature is 1500-2000° C., and the processing time is 10-60 min.

7. A high performance silicon carbide ceramic fiber membrane according to any one of claims 1 to 6, characterized in that: The high-performance silicon carbide ceramic fiber membrane is prepared from boron-containing compounds and organic silicon polymers through the steps of spinning, electron beam irradiation, infusibility, annealing, firing, and high-temperature sintering. The annealing temperature is 200-300° C., and the annealing time is 10-60 minutes.

8. The high performance silicon carbide ceramic fiber membrane according to claim 1, characterized in that: The high-performance silicon carbide ceramic fiber membrane has an oxygen content of ≤1.5wt% and a minimum reflection loss of ≤-35dB when the thickness is 1.5 to 3.0 mm.

9. A method for preparing a high-performance silicon carbide ceramic fiber membrane, characterized in that: The following steps are involved: Spinning raw materials to obtain raw fibers, wherein the raw materials include boron-containing compounds and organosilicon polymers; The fibrils are subjected to electron beam irradiation in an oxygen-containing atmosphere to infusibility treatment; Then it is fired and sintered at high temperature; The boron-containing compound is phenylboric acid or its derivatives, and the molecular structure of the phenylboric acid derivative is as follows: In the formula, R1 and R2 are independently selected from -(CH2) n CH2-, wherein n, x, and y are independently integers of 0 to 10.

10. The preparation method according to claim 9, characterized in that: The step also includes: after the electron beam irradiation infusibility treatment, annealing treatment is performed, the annealing temperature is 200-300° C., and the annealing time is 10-60 minutes.

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