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CN-121988240-A - Preparation method of SiBCN aerogel based on molecular-level doping of triethanolamine borate

CN121988240ACN 121988240 ACN121988240 ACN 121988240ACN-121988240-A

Abstract

The invention discloses a preparation method of SiBCN aerogel doped on the basis of triethanolamine borate molecular level, and belongs to the field of high-temperature-resistant thermal protection materials. According to the method, triethanolamine borate is used as a boron source and a nitrogen source, molecular-level uniform doping of boron and nitrogen elements is realized through a sol-gel process, and SiBCN aerogel is obtained after aging, modification and drying. The fiber felt can also be immersed in sol for synchronous gelation and post-treatment to prepare the composite material. The boron-nitrogen source molecular-level in-situ doping is used for generating high bond energy chemical bonds, so that shrinkage sintering of the material at high temperature is inhibited, and excellent heat insulation performance is maintained. After the fiber felt is introduced, the mechanical property is greatly improved, the compression strength of 50% compression deformation is 0.2-0.5MPa, the volume shrinkage rate of the material is extremely low (1-3%) at 1000-1100 ℃, and meanwhile, the material has a thermochromic function of deepening color along with the increase of heating time, so that a new material solution is provided for extreme environmental heat protection and post-disaster heat history tracing.

Inventors

  • ZHANG SHEN
  • CHEN WEI
  • YE JIHONG
  • YIN YUGUO
  • MA PENG
  • GAO WEIDONG
  • XU ZHIQIANG

Assignees

  • 中国矿业大学
  • 山东思达特测控设备有限公司

Dates

Publication Date
20260508
Application Date
20260316

Claims (9)

  1. 1. The preparation method of the SiBCN aerogel based on triethanolamine borate molecular level doping is characterized by comprising the following steps: (a) Mixing an organosilicon source, ethanol and deionized water, adding an acidic catalyst to adjust the mixed solution to be slightly acidic, and carrying out hydrolysis reaction under the conditions of water bath heating and stirring to obtain silica sol; (b) Mixing triethanolamine borate, ethanol and deionized water, and hydrolyzing under the condition of heating in a water bath to obtain boron-nitrogen sol; (c) Mixing the silica sol obtained in the step (a) with the boron-nitrogen sol obtained in the step (b), and stirring to obtain uniform SiBCN sol, wherein the molar ratio of the organosilicon source to the triethanolamine borate is 1:0.1-0.5; (d) Immersing the SiBCN wet gel into an aging liquid for aging, and immersing the SiBCN wet gel into a modifying liquid for hydrophobic modification after the aging is finished; (e) And (3) carrying out supercritical drying or vacuum freeze drying on the SiBCN wet gel treated in the step (d) to obtain SiBCN aerogel.
  2. 2. The method of preparing a molecular-level doped SiBCN aerogel based on triethanolamine borate according to claim 1, wherein in step (a), the organosilicon source is one or more selected from the group consisting of ethyl orthosilicate, methyl orthosilicate, trisaminopropyl triethoxysilane, vinyltrimethoxysilane, and dimethyldiethoxysilane; in the step (a), the molar ratio of the organic silicon source to the ethanol to the deionized water is 1:5-12:2-11, and in the step (b), the molar ratio of the triethanolamine borate to the ethanol to the deionized water is 1-5:10-30:10-30.
  3. 3. The preparation method of the SiBCN aerogel based on the molecular-level doping of the triethanolamine borate according to claim 1, wherein the hydrolysis temperature of the silica sol in the step (a) is 10-50 ℃, the hydrolysis time is 3-6 hours, the hydrolysis temperature of the boron-nitrogen sol in the step (b) is 40-75 ℃ and the hydrolysis time is 3-6 hours.
  4. 4. The SiBCN aerogel prepared by the preparation method of the SiBCN aerogel based on triethanolamine borate molecular level doping according to any one of claims 1-3, wherein the density of the SiBCN aerogel is 0.08-0.49 g/cm < 3 >, and the specific surface area is 350-1200 m < 2 >/g.
  5. 5. The preparation method of the SiBCN aerogel fiber reinforced composite material is characterized by comprising the following steps of: S1, providing a cleaned fiber mat; S2, immersing the fiber felt into SiBCN sol prepared by the method according to any one of claims 1-3, and standing for gel at normal temperature after vacuumizing treatment to obtain SiBCN gel fiber felt; s3, sequentially immersing the SiBCN gel fiber felt obtained in the step S2 into an aging liquid and a modifying liquid, and respectively performing aging treatment and hydrophobic modification treatment; S4, performing supercritical drying or vacuum freeze drying on the SiBCN gel fiber felt treated in the step S3 to obtain the SiBCN aerogel fiber reinforced composite material.
  6. 6. The preparation method of the SiBCN aerogel based on triethanolamine borate molecular level doping or the preparation method of the SiBCN aerogel fiber reinforced composite material according to claim 5, wherein the aging liquid is prepared from organosilane and absolute ethyl alcohol according to a volume ratio of 0.5-1.5:6-10, the modified liquid comprises polymethyl silane and absolute ethyl alcohol, the volume ratio of the polymethyl silane to the absolute ethyl alcohol is 0.5-2:8-12, and the polymethyl silane is one or more selected from hexamethyldisilazane, hexamethyldisiloxane and trimethylchlorosilane; aging for 24-48 hours in an aging liquid in an environment of 50-75 ℃; The hydrophobic modification condition is that the hydrophobic modification is carried out for 24-48 hours in a modification liquid environment at 50-75 ℃, liquid is replaced every 8-12 hours in the aging and modification process, and the volumes of the aging liquid and the modification liquid are respectively 1-5 times of the volume of the SiBCN wet gel.
  7. 7. The preparation method of the SiBCN aerogel based on the molecular-level doping of the triethanolamine borate or the preparation method of the SiBCN aerogel fiber reinforced composite material according to claim 5 is characterized in that supercritical drying adopts carbon dioxide as a drying medium, ethanol as an intermediate solvent, the drying temperature is 40-60 ℃, the drying pressure is 10-20 MPa, the drying time is 3-12 hours, the pre-cooling temperature of vacuum freeze drying is-85-50 ℃, the freezing time is 12-24 hours, the vacuum degree of the drying stage is 10-20 Pa, and the drying time is 24-48 hours.
  8. 8. The preparation method of the SiBCN aerogel fiber reinforced composite material is characterized in that in the step S1, the fiber felt is washed to be neutral by deionized water, ethanol and sodium hydroxide after being soaked for 5-10 hours, and then the fiber felt is dried, wherein the fiber felt is mullite fiber felt, high silica fiber felt or aluminum silicate fiber felt.
  9. 9. The SiBCN aerogel fiber reinforced composite material prepared by the preparation method of the SiBCN aerogel fiber reinforced composite material according to the claims 6-8 is characterized in that the thermal conductivity of the SiBCN aerogel fiber reinforced composite material at normal temperature is 0.0291-0.0324W/(m.K), the compressive strength is 0.2-0.5 MPa, the volume shrinkage rate of the SiBCN aerogel fiber reinforced composite material is 1-3% after the SiBCN aerogel fiber reinforced composite material is heated for 30min at 1000-1300 ℃, and the SiBCN aerogel fiber reinforced composite material has a thermochromic function, the color of a backfire surface is changed from light yellow to yellow brown under the high temperature effect of 700-1100 ℃, and the color depth deepens along with the increase of the heated time.

Description

Preparation method of SiBCN aerogel based on molecular-level doping of triethanolamine borate Technical Field The invention relates to the field of high-temperature-resistant heat-insulating materials, in particular to a preparation method of SiBCN aerogel based on molecular-level doping of triethanolamine borate. Background Aerogels exhibit excellent performance in the adiabatic field by virtue of their unique low density, high specific surface area, and ultra-high porosity microfeatures. The three-dimensional nano porous network structure built inside the solid phase heat conduction device obviously increases the tortuous path of solid phase heat conduction, and the nanoscale pore size limits the average free path of gas molecules, so that gas phase heat convection is effectively inhibited. Meanwhile, innumerable pore wall interfaces in the aerogel framework greatly attenuate radiant heat transfer through multiple scattering mechanisms. However, conventional silica aerogels are limited by lower sintering threshold temperatures, have poor thermodynamic stability at high temperature fields, and are prone to skeletal densification shrinkage and collapse of the pore structure. The agglomeration of the nano particles under high temperature driving causes coarsening of the aperture and sharp decrease of the specific surface area, thereby leading to rise of the heat conductivity and degradation of the heat insulation efficiency. In terms of mechanical properties, the extremely high porosity causes serious stress concentration phenomenon in the framework, and the material has high brittleness, low compressive strength and fragility due to the weak interface connection characteristic among particles, so that the service reliability of the material in a complex thermodynamic coupling environment is severely restricted. More importantly, existing high temperature resistant insulation materials often lack a discernible apparent physical response after experiencing a complex fire or thermal shock, and it is difficult to record thermal history by gradient changes in appearance. Particularly, the bridge cable has a high-rise and slender spatial configuration, the conventional means is difficult to reconstruct the distribution of the fire-receiving temperature in the three-dimensional space after disaster, so that the most severely damaged key parts are difficult to be positioned accurately, and the loss of key thermal history data buries a great blind area for the final judgment of the structural safety. Therefore, there is a need to solve the bottleneck problems of collapse of the high-temperature framework, remarkable mechanical brittleness, lack of thermal history indication function and the like of the traditional aerogel, develop a high-stability preparation technology integrating molecular element doping, in-situ reinforcement and macroscopic fiber synergistic reinforcement, and provide reliable material support for long-acting thermal protection of bridge cable structures in extreme thermal coupling environments. Disclosure of Invention The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, the invention aims to provide a preparation method of SiBCN aerogel based on molecular-level doping of triethanolamine borate, which innovatively introduces the triethanolamine borate rich in boron and nitrogen elements as a modification precursor. Under a high-temperature environment, the in-situ generated chemical bond of the reinforcement obviously solidifies the aerogel framework, and microstructure creep and hole collapse caused by high-temperature sintering are effectively inhibited, so that the thermal stability of the material is greatly improved, and meanwhile, the material has a thermochromic function at high temperature. The fiber reinforced phase is introduced to construct a composite system, so that the fracture toughness and the mechanical strength of the SiBCN aerogel fiber reinforced composite material are remarkably improved while the core advantage of low thermal conductivity is maintained, and the long-acting stable application of the SiBCN aerogel fiber reinforced composite material under extreme working conditions is realized. In order to solve the technical problems, the invention provides a preparation method of SiBCN aerogel based on triethanolamine borate molecular level doping, which comprises the following steps: (a) Mixing an organosilicon source, ethanol and deionized water, adding an acidic catalyst to adjust the mixed solution to be slightly acidic, and carrying out hydrolysis reaction under the conditions of water bath heating and stirring to obtain silica sol; (b) Mixing triethanolamine borate, ethanol and deionized water, and hydrolyzing under the condition of heating in a water bath to obtain boron-nitrogen sol; (c) Mixing the silica sol obtained in the step (a) with the boron-nitrogen sol obtained in the step (b), and stirring