A novel zero-convection high-insulation SiBN fiber aerogel and a preparation method thereof

Abstract

The application discloses a preparation method of novel zero-convection high-heat-insulation SiBN fiber aerogel, and specifically comprises the following steps: a novel zero-convection high-heat-insulation SiBN fiber aerogel is obtained through step-by-step calcination of hollow precursor fibers and hollow porous aerogel; the novel zero-convection high-heat-insulation SiBN fiber aerogel prepared by the application fully utilizes nanofibers as the support framework of the aerogel, and meanwhile, the hollow fibers are combined with the hollow microspheres of the gel to bond the uniform and dense nanopores and multistage fractal pores, so that the heat radiation and heat conduction are reduced, the heat insulation performance of the fibers is improved, the mechanical properties are improved after step-by-step calcination, the hollow porous fiber aerogel with high heat insulation is obtained, and the application prospect of the hollow porous fiber aerogel is wide in the fields of high-temperature insulation, high-temperature oxidation resistance and radar wave penetration.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of fiber aerogel preparation, and particularly relates to a novel zero-convection high-heat-insulation SiBN fiber aerogel and a preparation method thereof. BACKGROUND

[0002] Aerogel thermal insulation materials such as Fe2O3, Al2O3 and SiO2 have been widely used in the fields of aerospace, ship, oil and gas transportation, building thermal insulation and the like due to their high thermal insulation efficiency, temperature resistance, extremely low density, high porosity, specific surface area, low thermal and acoustic conductivity and the like. However, the aerogel thermal insulation materials have many problems in use, such as shape instability, easy collapse or deformation, poor stability at high temperature, easy pyrolysis, and the like. In addition, the porous structure of the aerogel material is a key factor affecting the thermal insulation performance and mechanical properties of the aerogel material. However, how to construct a suitable porous structure to obtain an aerogel material with high thermal insulation performance and certain mechanical properties has been a focus of researchers.

[0003] Sani et al. (Sani E, Mercatelli L, Sans J L, et al. Porous and dense hafnium and zirconium ultra-high temperature ceramics for solar receivers[J]. Optical Materials, 2013, 36(2): 163-168.) prepared porous ZrB2, HfC and HfB2 ceramics by partial sintering, and the porosities of the ceramics were 13%, 33% and 39% respectively, and the ceramics had good high-temperature oxidation resistance and mechanical properties. However, the porosities of the obtained porous ultra-high temperature ceramics were less than 50%, which limited the thermal insulation performance of the ceramics.

[0004] Chinese patent “Preparation method of silica aerogel for thermal insulation” (application number: CNCN201410085084.3, authorization number: CN103864081B, publication date: 2015.07.15) discloses a preparation method of silica aerogel for thermal insulation. The method comprises the following steps: firstly, preparing liquid water glass with a modifier; and then, reacting the liquid water glass with concentrated sulfuric acid to obtain the aerogel. The SiO2 particles of the aerogel are uniform and small, and the particles form a through hole structure. However, air convection occurs in the process of thermal insulation, which is not conducive to the thermal insulation performance of the aerogel.

[0005] Chinese patent "High-efficiency heat-insulating aerogel composite board and preparation method thereof" (Application No. CN201410779326.9, Authorization No. CN104496401B, Publication Date: 2016.09.14) discloses a high-efficiency heat-insulating aerogel composite board and a preparation method thereof. First, SiO2 sol is prepared, and then the sol is vacuum siphoned into a fiber felt to obtain an aerogel composite board. The aerogel composite board relies on the fiber felt to have good mechanical properties, but the fiber felt has a large density, which is not conducive to its heat-insulating performance, and the interface between the fiber felt and the SiO2 sol has a weak bonding, which may cause powder separation.

[0006] Chinese patent "Sound and heat-insulating aerogel foam composite material and preparation method thereof" (Application No. CN201711387572.X, Authorization No. CN108033764B, Publication Date: 2020.08.25) discloses a sound and heat-insulating aerogel foam composite material and a preparation method thereof. First, a sol and a gelatin solution are prepared, and then a surfactant and a moisture-proof agent are added to obtain an aerogel foam composite material. The process is simple, the raw materials are inexpensive, and the aerogel foam composite material can be prepared on a large scale. However, the aerogel foam composite material has a low porosity and a low mechanical property, which reduces the heat-insulating effect.

[0007] Chinese patent "Heat-insulating aerogel composite material and application thereof in sensor shell" (Application No. CN202310490032.3, Authorization No. CN116606481B, Publication Date: 2023.11.28) discloses a heat-insulating aerogel composite material and an application thereof in a sensor shell. First, a silicon source cellulose mixed solution is prepared, and then a heat-insulating aerogel composite material containing a hydrophobic wear-resistant and high-toughness shrinkage-resistant additive is prepared, which improves the service life of the aerogel. However, the organic matter is bonded to the aerogel skeleton, which has a high material density, reduces the use temperature and the heat-insulating effect of the aerogel. SUMMARY

[0008] The purpose of the present application is to provide a novel zero-convection high-heat-insulation SiBN fiber aerogel preparation method, which solves the problem of mechanical property and heat-insulating performance in the prior art that the addition of fiber reinforcing materials cannot effectively consider both properties.

[0009] The technical solution adopted by the present application is as follows:

[0010] A novel zero-convection high-heat-insulation SiBN fiber aerogel preparation method is implemented according to the following steps:

[0011] Step 1: Prepare a coaxial spinning solution

[0012] The spinning aid is dissolved in a mixed solution of ethanol and dilute nitric acid, the boric acid and silicon source are added to obtain the PBSO shell spinning solution; the boric acid is dissolved in deionized water at 75℃ to obtain a hot boric acid solution, the nitrogen source, spinning aid and paraffin are added to obtain the inner core spinning solution;

[0013] Step 2, synthesis of hollow precursor fiber

[0014] The PBSO shell spinning solution obtained in step 1 is placed in the shell layer push pump, the inner core spinning solution is placed in the core layer push pump, the spinning voltage, receiving distance, spinning temperature and humidity are adjusted, and the shell layer and core layer push pump speeds are controlled to synthesize the hollow precursor fiber;

[0015] Step 3, preparation of nanosol

[0016] The silicon source, styrene and azobisisobutyronitrile are ultrasonically mixed, dropped into a hydrochloric acid solution and stirred to react, NH3·H2O is added to adjust the pH value of the solution to 10, nitrogen is introduced and heated, and after centrifugation, alcohol washing is performed to obtain a core-shell powder, which is dispersed in deionized water, boric acid, nitrogen source, ethanol and hydrochloric acid solution are added, and stirring is performed to obtain a nanosol;

[0017] Step 4, preparation of hollow porous aerogel

[0018] The hollow precursor fiber prepared in step 2 is cut and added to the nanosol prepared in step 3, ultrasonic crushing and dispersion are performed, NH3·H2O is added, the pH value is adjusted to neutral, and freeze-drying is performed to obtain a nano hollow porous aerogel containing a three-dimensional network structure;

[0019] Step 5, step-by-step calcination treatment

[0020] The hollow porous aerogel prepared in step 4 is subjected to step-by-step calcination, first calcination in air atmosphere and heat preservation, then temperature increase and nitrogen calcination and heat preservation to obtain a SiBN fiber aerogel.

[0021] Further, the PBSO shell spinning solution prepared in step 1 is composed of the following substances by mass percentage: 0.4%~1% of the spinning aid, 20%~42% of ethanol, 10%~21% of dilute nitric acid with a concentration of 1 mol / L, 3.1%~3.7% of boric acid, and 32.3%~66.5% of the silicon source, the total of the above components being 100%, and the silicon source being one or more of ethyl silicate, methyl triethoxysilane and vinyl triethoxysilane.

[0022] Further, the inner core spinning solution prepared in step 1 is composed of the following substances by mass percentage: 3%~25% of boric acid, 35%~64% of deionized water, 3%~5% of the nitrogen source, 15%~25% of the spinning aid, and 15%~30% of paraffin, the total of the above components being 100%, and the nitrogen source being any one of urea and melamine.

[0023] Further, the assistant spinning agent in step 1 is one or more of polyvinylpyrrolidone, polyethylene oxide, and polyvinyl alcohol.

[0024] Further, the electrospinning parameters in step 2 are as follows: the spinning voltage is 20-26 kv, the receiving distance is 18-25 cm, the spinning temperature is 25 DEG C, the humidity is 30%, the shell layer propelling pump speed is 0.2-0.5 mL / h, and the core layer propelling pump speed is 0.15-0.3 mL / h.

[0025] Further, the core-shell powder prepared in step 3 is composed of the following components in mass percentage: 4.54-4.59% silicon source, 4.54-4.59% styrene, 0.02-0.22% azobisisobutyronitrile, and 90.6-90.9% hydrochloric acid solution with a pH of 3.5, the total of the above components being 100%, the silicon source being one or more of ethyl silicate, vinyltriethoxysilane, and methyltriethoxysilane, the stirring reaction time being 0.5-1 h, the heating temperature being 75 DEG C, the centrifugal speed being 4000 rpm, the centrifugal time being 15 min, the prepared nanosol being composed of the following components in mass percentage: 5-8% core-shell powder, 20-23% deionized water, 5-10% boric acid, 3-5% nitrogen source, 44-62% ethanol, and 5-10% hydrochloric acid with a concentration of 12 mol / L, the total of the above components being 100%, the nitrogen source being any one of urea and melamine.

[0026] Further, the ultrasonic crushing and dispersion parameters in step 4 are as follows: ultrasonic crushing for 1 h at 40 Hz, and the freeze-drying parameters are as follows: freezing for 12 h at -40 DEG C, and drying for 48-72 h at -40 DEG C under a vacuum of 5-20 Pa.

[0027] Further, the specific method of step 5 is as follows: the hollow porous aerogel prepared in step 4 is calcined in air at 400-600 DEG C for 1-3 h, and then calcined in nitrogen at 900-1000 DEG C for 1-3 h, to obtain the hollow porous SiBN fiber aerogel.

[0028] The SiBN fiber aerogel is prepared according to the above-mentioned preparation method of a novel zero-convection high-heat-insulation SiBN fiber aerogel.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] The application discloses a preparation method of novel zero-convection high-heat-insulation SiBN fiber aerogel. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Figure 1 is a schematic diagram of a cross-sectional morphology of novel zero-convection high-heat-insulation SiBN fiber aerogel prepared by example 1 of the application. DETAILED DESCRIPTION

[0032] The application will be described in detail below in combination with the drawings and specific embodiments.

[0033] A preparation method of novel zero-convection high-heat-insulation SiBN fiber aerogel, which is specifically implemented according to the following steps:

[0034] Step 1, preparation of coaxial spinning solution

[0035] The spinning aid is dissolved in a mixed solution of ethanol and dilute nitric acid with a concentration of 1 mol / L, and boric acid and a silicon source are added, which are composed of the following substances by mass percentage: 0.4% to 1% of the spinning aid, 20% to 42% of ethanol, 10% to 21% of dilute nitric acid, 3.1% to 3.7% of boric acid, and 32.3% to 66.5% of the silicon source, and the total of the above components is 100%. The silicon source is one or more of ethyl silicate, methyl triethoxysilane and vinyl triethoxysilane, and a shell spinning solution is prepared.

[0036] The boric acid is dissolved in deionized water at 75 DEG C, and a nitrogen source, a spinning aid and paraffin are added, and the inner core spinning solution is composed of the following substances by mass percentage: 3% to 25% of boric acid, 35% to 64% of deionized water, 3% to 5% of the nitrogen source, 15% to 25% of the spinning aid, and 15% to 30% of paraffin, and the total of the above components is 100%. The nitrogen source is any one of urea and melamine, and the spinning aid is any one of polyvinylpyrrolidone, polyoxyethylene and polyvinyl alcohol.

[0037] Step 2, synthesis of hollow precursor fiber

[0038] The shell spinning solution obtained in step 1 is placed into a shell push pump, and the core spinning solution is placed into a core push pump, the spinning voltage is adjusted to 20-26kv, the receiving distance is 18cm-25cm, the spinning temperature is 25℃, the humidity is 30%, the speed of the shell push pump is 0.2mL / h-0.5mL / h, the speed of the core push pump is 0.15mL / h-0.3mL / h, and the electrostatic spinning is performed to obtain a precursor fiber.

[0039] Step 3, preparation of nanosol

[0040] The silicon source, styrene and azobisisobutyronitrile are ultrasonically mixed, and then dropped into a hydrochloric acid solution for stirring reaction. The mixture is composed of the following components by mass percentage: silicon source 4.54%-4.59%, styrene 4.54%-4.59%, azobisisobutyronitrile 0.02%-0.22%, hydrochloric acid solution 90.6%-90.9%, and pH 3.5. The total of the above components is 100%. The silicon source is one or more of methyltriethoxysilane, vinyltriethoxysilane and methyltriethoxysilane. The pH of the hydrochloric acid solution is 3.5, and the reaction time is 0.5h-1h. NH3·H2O is added to adjust the pH of the solution to 10, nitrogen is introduced, and heating is performed at a temperature of 75℃. The centrifugal speed is 4000rpm, the centrifugal time is 15min, and the core-shell powder is obtained by alcohol washing. The core-shell powder is dispersed in deionized water, boric acid, nitrogen source, ethanol and hydrochloric acid solution are added, and stirring is performed to obtain a nanosol. The nanosol is composed of the following components by mass percentage: core-shell powder 5%-8%, deionized water 20%-23%, boric acid 5%-10%, nitrogen source 3%-5%, ethanol 44%-62%, hydrochloric acid 5%-10% with a concentration of 12mol / L, and the total of the above components is 100%. The nitrogen source is any one of urea and melamine.

[0041] Step 4, preparation of hollow porous aerogel

[0042] The hollow precursor fiber prepared in step 2 is cut and added to the nanosol prepared in step 3. Ultrasonic dispersion is performed for 1h at 40Hz, NH3·H2O is added, the pH is adjusted to neutral, and then freezing is performed at-40℃ for 12h. Drying is performed at-40℃ under vacuum at a pressure of 5-20Pa for 48h-72h to obtain a nano hollow porous aerogel containing a three-dimensional network structure.

[0043] Step 5, step-by-step calcination

[0044] The hollow porous aerogel prepared in step 4 is subjected to step-by-step calcination. The calcination is performed in an air atmosphere at 400℃-600℃ for 1-3h, and in a nitrogen atmosphere at 900℃-1000℃ for 1-3h to obtain a hollow porous SiBN fiber aerogel.

[0045] The application obtains hollow precursor fibers by controlling the concentration of the spinning solution of the coaxial electrospinning inner core, the spinning propulsion speed and adding phase change materials, improves the heat insulation performance of the aerogel fiber composition unit; adjusts the preparation of nano SiO2 hollow spheres with a certain hollow structure on the basis of in-situ polymerization by controlling styrene nucleation, reduces the air convection effect of the obtained aerogel in the heat insulation application process; and adjusts the composition of the hollow fiber and the hollow microsphere, and bonds to form a fiber aerogel material with uniform nanopores and multi-level fractal channels. While improving the heat insulation performance, the hollow fiber serves as the aerogel support skeleton, and after step-by-step calcination, the precursor fiber is converted into a hollow porous SiBN fiber aerogel, which relieves the interfacial tension between the nanopores and the gel skeleton, weakens the shrinkage of the material, and improves the overall mechanical properties.

[0046] The novel zero-convection high-heat-insulation SiBN fiber aerogel prepared by the application fully utilizes the nano fiber as the support skeleton of the aerogel, and at the same time, the hollow fiber is compounded with the hollow microsphere of the gel to bond and form uniform nanopores and multi-level fractal channels, reduces heat radiation and heat conduction, improves the heat insulation performance of the fiber, improves the mechanical properties after step-by-step calcination, and obtains a hollow porous fiber aerogel with high heat insulation, which has a wide application prospect in the fields of high-temperature insulation, high-temperature oxidation resistance, radar wave transmission and the like.

[0047] Example 1

[0048] 0.04g of polyoxyethylene powder was dissolved in a mixed solution of 4g of ethanol and 2g of dilute nitric acid, 0.31g of boric acid was added and stirred for 0.5h, and finally 2.5g of ethyl silicate and 2.9g of methyl triethoxysilane were added to obtain a PBSO shell spinning solution; 9g of boric acid was dissolved in 33mL of 75℃ deionized water to obtain a hot boric acid solution, which was heated to 95℃, 3g of melamine, 30g of paraffin and 25g of polyvinyl alcohol were added and stirred for 2h to obtain an inner core spinning solution.

[0049] The spinning solution obtained in step 1 was placed in a propulsion pump, the spinning voltage was adjusted to 20kv, the receiving distance was 18cm, the spinning temperature was 25℃, the humidity was 30%, the shell layer propulsion pump speed was 0.2mL / h, and the core layer propulsion pump speed was 0.15mL / h, and the electrospinning obtained the precursor fiber.

[0050] Mix 2.27 g methyl triethoxysilane, 2.27 g styrene, 0.01 g azobisisobutyronitrile under ultrasonic at 40 Hz for 5 min, add 45.3 mL hydrochloric acid solution, stir at 250 rpm for 1 h, add NH3·H2O to adjust the pH value to 10, reduce the stirring rate to 150 rpm and react for 50 min, pass nitrogen to heat to 75℃ and polymerize for 1 h, centrifuge the above mixture at 4000 rpm for 15 min, wash with ethanol to obtain a core-shell powder, disperse in 10 mL deionized water, add 2 g boric acid, 2 g melamine, 28.5 mL ethanol, 5 mL hydrochloric acid,

[0051] Cut the hollow precursor fiber prepared in step 2, add to the nanosol prepared in step 3, disperse under ultrasonic at 40 Hz for 1 h, add NH3·H2O, adjust the pH value to neutral, freeze at -40℃ for 12 h, dry at -40℃ under vacuum at 20 Pa for 48 h, and obtain a nanohollow porous aerogel containing a three-dimensional network structure.

[0052] Step 4: The hollow porous aerogel prepared in step 4 is calcined in steps, heat at 400℃ in air for 3 h, and calcine at 900℃ in nitrogen for 3 h, to obtain a hollow porous SiBN fiber aerogel.

[0053] Figure 1 Figure 1 is a schematic diagram of the cross-sectional morphology of the new zero-convection high-thermal-insulation SiBN fiber aerogel prepared in Example 1. From the figure, it can be seen that the fiber is successfully crosslinked to form a three-dimensional structure after aerogel treatment, and the interface between the two is tight. Figure 1

[0054] Table 1 is a comparison of the thermal insulation performance of Example 1 with SiOC aerogel and BN aerogel. From Table 1, it can be seen that the SiOC aerogel has the largest density and the best compressive strength due to the presence of C and O, but has the smallest specific surface area and the highest thermal conductivity, resulting in poor thermal insulation performance. The specific surface area of the BN aerogel increases, the thermal conductivity decreases, the thermal insulation performance is good, and the density decreases, but the weak bonding of the material leads to the worst compressive strength. Example 1 improves the mechanical properties of the aerogel structure by fiber reinforcement, and the hollow structure of the fiber combined with the aerogel forms a hollow porous structure, which reduces the density of the material and increases the specific surface area, resulting in the smallest thermal conductivity of the material and excellent thermal insulation performance.

[0055] Table 1

[0056] Sample Thermal conductivity W m -1 ∙ K -1 ]]> Specific surface area m 2∙ g -1 ]]> Density g-cm -3 ]] Compressive strength MPa Example 1 0.025 75 0.67 4.53 SiOC aerogel 0.058 42 0.90 2.11 BN aerogel 0.051 54 0.86 0.52

[0057] Example 2

[0058] ​A PBSO shell spinning solution was prepared by dissolving 0.1 g of polyethylene glycol powder in a mixed solution of 4.2 g of ethanol and 2.1 g of dilute nitric acid, adding 0.37 g of boric acid and stirring for 0.5 h, and finally adding 1.6 g of ethyl silicate and 1.63 g of methyl triethoxysilane; a core spinning solution was prepared by dissolving 3 g of boric acid in 25 mL of deionized water at 75 °C, adding 3 g of melamine, 15 g of paraffin and 25 g of polyvinyl alcohol, stirring for 2 h, and then heating to 95 °C.

[0059] The spinning solution obtained in step 1 was placed in a push pump, the spinning voltage was adjusted to 20 kV, the receiving distance was 18 cm, the spinning temperature was 25 °C, the humidity was 30%, the shell push pump speed was 0.2 mL / h, and the core push pump speed was 0.15 mL / h, and electrospinning was performed to obtain a precursor fiber.

[0060] A mixture of 2.295 g of ethyl silicate, 2.295 g of styrene and 0.01 g of azobisisobutyronitrile was ultrasonically mixed at 40 Hz for 5 min, 45.4 mL of a hydrochloric acid solution was added, stirring was performed at 250 rpm for 1 h, NH3·H2O was added to adjust the pH value to 10, the stirring rate was reduced to 150 rpm, reaction was performed for 50 min, nitrogen was introduced, heating was performed to 75 °C, and polymerization was performed for 1 h; the above mixture was centrifuged at 4000 rpm for 15 min, washed with ethanol, and then dispersed in 10 mL of deionized water, 2.5 g of boric acid, 1.5 g of melamine, 22 mL of ethanol and 2.5 mL of hydrochloric acid were added.

[0061] The hollow precursor fiber prepared in step 2 was cut and added to the nanosol prepared in step 3, ultrasonic dispersion was performed at 40 Hz for 1 h, NH3·H2O was added to adjust the pH value to neutral, and then freezing was performed at -40 °C for 12 h; vacuumization was performed at -40 °C, and drying was performed at 5 Pa for 72 h to obtain a nano hollow porous aerogel containing a three-dimensional network structure.

[0062] The hollow porous aerogel prepared in step 4 was step-by-step calcined, heat preservation was performed at 600 °C in an air atmosphere for 3 h, and calcination was performed at 1000 °C in a nitrogen atmosphere for 3 h to obtain a hollow porous SiBN fiber aerogel.

[0063] Example 3

[0064] A PBSO shell spinning solution was prepared by dissolving 0.1 g of polyethylene glycol powder in a mixed solution of 4.2 g of ethanol and 2.1 g of dilute nitric acid, adding 0.37 g of boric acid and stirring for 0.5 h, and finally adding 1.6 g of ethyl silicate and 1.63 g of methyl triethoxysilane; a core spinning solution was prepared by dissolving 3 g of boric acid in 25 mL of deionized water at 75 °C, adding 3 g of melamine, 15 g of paraffin and 25 g of polyvinyl alcohol, stirring for 2 h, and then heating to 95 °C.

[0065] The spinning solution obtained in step 1 was placed into a push pump, the spinning voltage was adjusted to 20kv, the receiving distance was 18cm, the spinning temperature was 25℃, the humidity was 30%, the shell push pump speed was 0.2mL / h, the core push pump speed was 0.15mL / h, and the precursor fiber was obtained by electrospinning.

[0066] 2.295g of vinyl triethoxysilane, 2.295g of styrene, and 0.11g of azobisisobutyronitrile were ultrasonically mixed at 40Hz for 5min, 45.45mL of hydrochloric acid solution was added, stirring was carried out at 250rpm for 0.5h, NH3·H2O was added to adjust the pH value to 10, the stirring rate was reduced to 150rpm, reaction was carried out for 50min, nitrogen was introduced, heating was carried out to 75℃, and polymerization was carried out for 1h, the above mixture was centrifuged at 4000rpm for 15min, ethanol washing was carried out to obtain a core-shell powder, the powder was dispersed in 11.5mL of deionized water, 5g of boric acid, 2.5g of melamine, 31mL of ethanol, and 5mL of hydrochloric acid were added.

[0067] The hollow precursor fiber prepared in step 2 was cut and added to the nanosol prepared in step 3, ultrasonic dispersion was carried out at 40Hz for 1h, NH3·H2O was added to adjust the pH value to neutral, freezing was carried out at-40℃ for 12h, vacuumizing was carried out at-40℃, and drying was carried out at 10Pa for 50h to obtain a nano hollow porous aerogel containing a three-dimensional network structure.

[0068] The hollow porous aerogel prepared in step 4 was step-by-step calcined, 500℃ air atmosphere was maintained for 3h, 900℃ nitrogen atmosphere was calcined and maintained for 2h to obtain a hollow porous SiBN fiber aerogel.

[0069] Example 4

[0070] 0.1g of polyoxyethylene powder was dissolved in a mixed solution of 4.2g of ethanol and 2.1g of dilute nitric acid, 0.37g of boric acid was added and stirred for 0.5h, and finally 6.65g of vinyl triethoxysilane was added to obtain a PBSO shell spinning solution; 9g of boric acid was dissolved in 43mL of deionized water at 75℃ to obtain a hot boric acid solution, heating was carried out to 95℃, 3g of urea, 25g of paraffin, and 20g of polyoxyethylene were added, and stirring was carried out for 2h to obtain an inner core spinning solution.

[0071] The spinning solution obtained in step 1 was placed into a push pump, the spinning voltage was adjusted to 20kv, the receiving distance was 18cm, the spinning temperature was 25℃, the humidity was 30%, the shell push pump speed was 0.2mL / h, the core push pump speed was 0.15mL / h, and the precursor fiber was obtained by electrospinning.

[0072] 2.25 g methyl triethoxysilane, 2.25 g styrene, 0.05 g azobisisobutyronitrile were mixed under ultrasonic at 40 Hz for 5 min, 45.4 mL hydrochloric acid solution was added, stirred at 250 rpm for 1 h, NH3·H2O was added to adjust the pH value to 10, the stirring rate was reduced to 150 rpm and reacted for 50 min, nitrogen was introduced and heated to 75℃ for polymerization for 1 h, the above mixture was centrifuged at 4000 rpm for 15 min, washed with ethanol to obtain a core-shell powder, which was dispersed in 10 mL deionized water, 6 g boric acid, 2 g urea, 29.5 mL ethanol and 5 mL hydrochloric acid were added.

[0073] The hollow precursor fiber prepared in step 2 was cut and added to the nanosol prepared in step 3, dispersed under ultrasonic at 40 Hz for 1 h, NH3·H2O was added to adjust the pH value to neutral, then frozen at-40℃ for 12 h, dried at-40℃ under vacuum at 10 Pa for 72 h to obtain a nanohollow porous aerogel containing a three-dimensional network structure.

[0074] The hollow porous aerogel prepared in step 4 was step-by-step calcined, heat-treated at 600℃ in air for 1 h, and calcined at 1000℃ in nitrogen for 1 h to obtain a hollow porous SiBN fiber aerogel.

[0075] The above-described embodiments only express the specific implementation of the present application, which is described in more detail and in more detail, but it cannot be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A method for preparing a novel zero-convection highly thermally insulated SiBN fiber aerogel, characterized by, The method is implemented according to the following steps: Step 1, preparing a coaxial spinning solution The spinning aid is dissolved in a mixed solution of ethanol and dilute nitric acid, and boric acid and a silicon source are added to obtain a PBSO shell spinning solution; the boric acid is dissolved in deionized water at 75 DEG C to obtain a hot boric acid solution, and a nitrogen source, a spinning aid and paraffin are added to obtain an inner core spinning solution; Step 2, synthesizing a hollow precursor fiber The PBSO shell spinning solution obtained in step 1 is placed in a shell layer push pump, and the inner core spinning solution is placed in a core layer push pump; the spinning voltage, receiving distance, spinning temperature and humidity are adjusted, and the speeds of the shell layer and core layer push pumps are controlled to synthesize a hollow precursor fiber; Step 3, preparing a nano sol The silicon source, styrene and azobisisobutyronitrile are ultrasonically mixed, and then dropped into a hydrochloric acid solution for stirring and reaction; NH3H2O is added to adjust the pH value of the solution to 10; nitrogen is introduced and heated; after centrifugation, the alcohol is washed to obtain a core-shell powder, which is dispersed in deionized water; boric acid, a nitrogen source, ethanol and a hydrochloric acid solution are added and stirred to obtain a nano sol; Step 4, preparing a hollow porous aerogel The hollow precursor fiber prepared in step 2 is cut and added to the nano sol prepared in step 3, and then ultrasonic broken dispersion is performed; after the pH value is adjusted to neutral, freeze drying is performed to obtain a nano hollow porous aerogel containing a three-dimensional network structure; Step 5, step-by-step calcination treatment The hollow porous aerogel prepared in step 4 is subjected to step-by-step calcination, first calcined in an air atmosphere and then heated and calcined in a nitrogen atmosphere to obtain a SiBN fiber aerogel.

2. A process for the preparation of a novel zero-convection highly thermally insulated SiBN fibrous aerogel according to claim 1, characterized by, The PBSO shell spinning solution prepared in step 1 is composed of the following substances by mass percentage: 0.4% to 1% of a spinning aid, 20% to 42% of ethanol, 10% to 21% of dilute nitric acid with a concentration of 1 mol / L, 3.1% to 3.7% of boric acid, and 32.3% to 66.5% of a silicon source; the total of the above components is 100%; the silicon source is one or more of ethyl silicate, methyl triethoxysilane and vinyl triethoxysilane.

3. The method for preparing a novel zero-convection, high-thermal-insulation SiBN fiber aerogel according to claim 1, characterized in that, The inner core spinning solution prepared in step 1 is composed of the following substances by mass percentage: 3% to 25% of boric acid, 35% to 64% of deionized water, 3% to 5% of a nitrogen source, 15% to 25% of a spinning aid, and 15% to 30% of paraffin; the total of the above components is 100%; the nitrogen source is any one of urea and melamine.

4. The method for preparing a novel zero-convection, high-thermal-insulation SiBN fiber aerogel according to claim 1, characterized in that, The spinning aid in step 1 is one or more of polyvinylpyrrolidone, polyethylene oxide and polyvinyl alcohol.

5. The method for preparing a novel zero-convection, high-thermal-insulation SiBN fiber aerogel according to claim 1, characterized in that, The electrospinning parameters in step 2 are as follows: the spinning voltage is 20 to 26 kv, the receiving distance is 18 cm to 25 cm, the spinning temperature is 25 DEG C, the humidity is 30%, the speed of the shell layer push pump is 0.2 mL / h to 0.5 mL / h, and the speed of the core layer push pump is 0.15 mL / h to 0.3 mL / h.

6. The method for preparing a novel zero-convection, high-thermal-insulation SiBN fiber aerogel according to claim 1, characterized in that, The core-shell powder prepared in step 3 consists of the following components by mass percentage: 4.54% to 4.59% of a silicon source, 4.54% to 4.59% of styrene, 0.02% to 0.22% of azobisisobutyronitrile, 90.6% to 90.9% of a hydrochloric acid solution with a pH of 3.5, and the total of the above components is 100%, wherein the silicon source is one or more of ethyl silicate, vinyltriethoxysilane, and methyltriethoxysilane, the stirring reaction time is 0.5 to 1 h, the heating temperature is 75°C, the centrifugation rate is 4000 rpm, the centrifugation time is 15 min, and the nano sol is prepared according to the following components by mass percentage: 5% to 8% of the core-shell powder, 20% to 23% of deionized water, 5% to 10% of boric acid, 3% to 5% of a nitrogen source, 44% to 62% of ethanol, and 5% to 10% of hydrochloric acid with a concentration of 12 mol / L, and the total of the above components is 100%, wherein the nitrogen source is any one of urea and melamine.

7. The method for preparing a novel zero-convection, high-thermal-insulation SiBN fiber aerogel according to claim 1, characterized in that, The ultrasonic crushing and dispersion parameters in step 4 are: ultrasonic crushing for 1 h at 40 Hz, and the freeze-drying parameters are: freezing at -40°C for 12 h, and then drying at -40°C under a vacuum condition of 5 to 20 Pa for 48 h to 72 h.

8. A novel process for the preparation of zero convective high thermal insulation SiBN fibrous aerogels according to claim 1, characterized by, The specific method of step 5 is: step-by-step calcination of the hollow porous aerogel prepared in step 4, calcination in an air atmosphere at 400°C to 600°C for 1 to 3 h, and calcination in a nitrogen atmosphere at 900°C to 1000°C for 1 to 3 h, to obtain a hollow porous SiBN fiber aerogel.

9. The SiBN fiber aerogel prepared by the preparation method of a novel zero-convection high-insulation SiBN fiber aerogel according to any one of claims 1 to 8.

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