CN110760291A - Preparation method of silicate high-temperature wave-absorbing composite material - Google Patents

Preparation method of silicate high-temperature wave-absorbing composite material Download PDF

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CN110760291A
CN110760291A CN201911055121.5A CN201911055121A CN110760291A CN 110760291 A CN110760291 A CN 110760291A CN 201911055121 A CN201911055121 A CN 201911055121A CN 110760291 A CN110760291 A CN 110760291A
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composite material
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alcohol
silicon source
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李季
刘继鹏
张磊
杨春晖
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Harbin Institute of Technology
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Abstract

A preparation method of a silicate high-temperature wave-absorbing composite material relates to a preparation method of a composite material, and belongs to the field of wave-absorbing materials. The invention aims to solve the technical problems of complex processing, higher cost and lower wave absorption performance of the existing wave absorbing material. The method comprises the following steps: SiO 22Synthesizing aerogel; second, high temperature synthesis of SiO2-ferrite composite material to obtain SiC-ferrite/carbonaceous material high temperature wave-absorbing composite material; the method has simple preparation processThe operation is simple and convenient, the equipment requirement is low, and the yield is high; the silicon source and the metal salt are cheap and easily available, and the shapes of aerogel and ferrite can be changed by adjusting the concentrations of the silicon source and nickel salt, iron salt or cobalt salt; the wave-absorbing composite material has the advantages of high dielectric loss, thin thickness and low density, and the reflection loss of the wave-absorbing composite material is lower than-5 dB and the maximum reflection loss reaches-14 dB in a specific microwave frequency band such as an X band (8-12GHz) and a Ku band (12-18 GHz). Meanwhile, the wave-absorbing strength and the wave-absorbing frequency band are controllable.

Description

Preparation method of silicate high-temperature wave-absorbing composite material
Technical Field
The invention relates to a preparation method of a composite material, and belongs to the field of wave-absorbing materials.
Background
The rapid development of sol-gel technology over the last two decades has led to a rapid development of synthetic porous materials, which technology complements the conventional methods of preparing amorphous solids or glasses. The porous material has the characteristics of high specific surface area, high porosity, adjustable skeleton and the like, so the porous material has extremely important significance in various applications such as adsorption, sensing, wave absorption and the like. Aerogel is a new miraculous material in the 21 st century, and although solid, 99% of the components are composed of gas. The lightest silica aerogel at present is only 3mg/cm3Three times heavier than air. Among all the known solid porous materials, aerogels are known for their small pore size, large specific surface area and excellent optical transmittance. Further, in all aerogels, SiO2Aerogels have outstanding properties.
In 1931, aerogel was first prepared by professor s.s.kistler of stanford university, usa, who obtained SiO by supercritical drying method (ethanol as supercritical drying medium) using water glass as silicon source2Aerogels, because of their very low density and bluish appearance, have the external sign "blue smoke". Subsequently, the Kistler professor produced aerogels based on aluminum, chromium, tin, and the like, and discussed the properties of the aerogels in detail. Although Kistler teaches that aerogels have promising prospects in the fields of thermal insulation, catalysis, etc., the preparation process of aerogels is complicated, and people pay no attention to the aerogel production process. Until the late 70 s of the 20 th century, sol-gel technology was developed and used in the preparation of gels, which resulted in uniform dispersion of the silicon source in the solvent to give a uniform gel. Professor Stanislas Teichner, Claud Bernard university, France, uses tetramethyl silicate (TMOS) as a silicon source and methanol as a solvent by sol-gelThe alcogel is obtained by one step by a glue method, and then the high-quality SiO is prepared by supercritical drying2An aerogel. From this, SiO2Aerogels have entered a rapid development era. Later, the Peri group used methanol as a supercritical drying medium to dry the hydrogel, greatly shortened the drying cycle, and further promoted the research of aerogel. In 1974, Cantin et al treated SiO2The aerogel is applied to a Cerenkov detector for collecting space particles. Thereafter, SiO in Europe2The aerogel is arranged in the inner layer of the double-sided window for heat preservation and energy storage. Tewari used carbon dioxide as a supercritical drying medium in 1985, successfully carried out the drying of wet gels, driving SiO2Commercialization of aerogels has progressed. Reports about the application of the aerogel to high-efficiency heat-insulating materials, high-efficiency rechargeable batteries and the like appear later, and the wide interest of scientific researchers is aroused. Aerogels have been used or considered for thermal insulation, catalyst and space dust collection, etc. since then.
In most cases, solid particle absorbents such as ferrite, metal powder, ceramic, carbon nano-particles and the like are widely used for preparing wave-absorbing composite materials. Although the wave-absorbing performance is general, most of the wave-absorbing materials have not been practically applied due to the defects of large density, poor stability, large loading capacity and the like. And the existing material has complex processing method, higher cost and poor wave-absorbing effect. With the demand for functional diversification of composite materials in aerospace vehicles, ultra-lightweight and thermal insulation of aerogel materials is no longer the only goal sought. In order to ensure the normal operation of internal electronic components or the requirement of self orbit invisibility, the shuttle aerospace craft in a complex electromagnetic environment needs to absorb or shield useless or hostile electromagnetism. Therefore, an aerogel material with wave-absorbing performance is needed to meet the demand of the aerospace field for functional diversification of aerogel materials.
Disclosure of Invention
The invention aims to solve the technical problems of complex processing, higher cost and lower wave absorption performance of the existing wave absorbing material, and provides a preparation method of a silicate high-temperature wave absorbing composite material.
The preparation method of the silicate high-temperature wave-absorbing composite material comprises the following steps:
SiO 22Synthesis of aerogel:
a. mixing a silicon source, an alcohol solvent, N-dimethylformamide and hydrochloric acid according to a molar ratio of (1-5) to 1: 1, then hydrolyzing at 90-100 ℃, and cooling to room temperature after hydrolysis is completed;
b. dropwise adding alkali liquor and stirring for 30-60 minutes to perform polycondensation reaction, wherein the volume ratio of the alkali liquor to the hydrochloric acid is 1-2: 1;
c. transferring the solution in the step b into a mold, sealing, and then putting into an oven with the temperature of 35-50 ℃ for aging for 6-12 hours;
d. soaking the gel in an alcohol solution for 15 hours, and then soaking the gel in a mixed solution of a silicon source solution and the alcohol solution for 24 hours to obtain wet gel;
e. soaking the wet gel in ethanol in an oven at 50 deg.C for 6-12 hr to remove water and silicon source, replacing ethanol with n-hexane, adding modifying solution at molar ratio of 1-2: 1, and sealing to obtain gel;
second, high temperature synthesis of SiO2-ferrite composite material:
f. mixing a silane coupling agent, soluble salt for preparing ferrite, the gel obtained in the step e, an alcohol solvent and deionized water, stirring for 1-2 hours, and ultrasonically dispersing for 30-60 minutes to obtain a mixed solution, wherein the volume percentage concentration of the silane coupling agent in the mixed solution is 0.25-0.5%;
the molar ratio of the gel obtained in the step e to soluble salt for preparing ferrite is 1: 1-2;
the ratio of the gel obtained in the step e to the alcohol solvent is 1g to (40-60) mL;
the ratio of the gel obtained in the step e to the deionized water is 1g to (40-60) mL;
g. transferring the mixed solution obtained in the step f into a high-temperature reaction kettle, heating to 80-120 ℃ at the speed of 2-4 ℃/min, preserving heat for 4-6 h, after the reaction is finished, exchanging and centrifugally cleaning with water and an alcohol solution, washing wet gel with n-hexane, and drying in vacuum to obtain the composite aerogel;
h. under the condition of air or nitrogen, the composite aerogel is placed in a 350-450 ℃ tubular furnace to be roasted for 2-4 h, and then is cooled to room temperature, so that the SiC-ferrite/carbonaceous material high-temperature wave-absorbing composite material is obtained;
the soluble salt for preparing the ferrite in the second step is ferric salt, cobalt salt or nickel salt;
the nickel salt is one or more of nickel chloride hexahydrate, nickel sulfate hexahydrate and nickel nitrate hexahydrate;
the ferric salt is one or more of ferric chloride hexahydrate, ferrous sulfate heptahydrate and ferric nitrate nonahydrate;
the cobalt salt is one or more of cobalt chloride hexahydrate, cobalt sulfate heptahydrate and cobalt nitrate hexahydrate;
the alcohol solvent in the step two f is one or more of ethanol, methanol, propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, cyclobutanol, cyclohexanol, cyclopentanol, isobutanol and isoamylol.
In step one a, the silicon source is methyl orthosilicate, ethyl orthosilicate, Tetramethoxysilane (TMOS), Tetraethoxysilane (TEOS), Polyethoxydisiloxane (PEDS), or methyltrimethoxysilane (MTMS).
In the step one a, the alcohol solvent is one or more of ethanol, methanol, propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, cyclobutanol, cyclohexanol, cyclopentanol, isobutanol and isoamylol.
In the step one b, the alkali liquor is aqueous solution of ammonia water, sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, disodium hydrogen phosphate, sodium citrate or potassium citrate.
In the step one, the alcohol solution mixed solution is water solution of two or more of ethanol, methanol, propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, cyclobutanol, cyclohexanol, cyclopentanol, isobutanol and isoamylol.
In the step one d, the molar ratio of the silicon source solution to the alcohol solution mixed solution in the silicon source solution and the alcohol solution mixed solution is 1-3: 1.
In the step one d, the silicon source solution is an aqueous solution of silicon source of methyl orthosilicate, ethyl orthosilicate, Tetramethoxysilane (TMOS), Tetraethoxysilane (TEOS), polyethoxy disiloxane (PEDS) or methyltrimethoxysilane (MTMS).
In the first step e, the modified liquid is Hexamethyldisilazane (HMDZ) or Trimethylchlorosilane (TMCS).
The silane coupling agent in the second step f is KH-550, KH-540, KH-560, KH-792 or KH-6020.
In the second step, the temperature of vacuum drying is 60-80 ℃ and the time is 12-24 h.
The novel silicate high-temperature wave-absorbing composite material has the following advantages:
1. the preparation process is simple, the operation is simple and convenient, the equipment requirement is low, and the yield is high;
2. the silicon source and the metal salt are cheap and easily available, and the shapes of aerogel and ferrite can be changed by adjusting the concentrations of the silicon source and nickel salt, iron salt or cobalt salt;
3. the wave-absorbing composite material has the advantages of high dielectric loss, thin thickness and low density, and the reflection loss of the wave-absorbing composite material is lower than-5 dB and the maximum reflection loss reaches-14 dB in a specific microwave frequency band such as an X band (8-12GHz) and a Ku band (12-18 GHz). Meanwhile, the wave-absorbing strength and the wave-absorbing frequency band are controllable.
Drawings
FIG. 1 is an SEM photograph of a silicate high-temperature wave-absorbing composite material in experiment I;
FIG. 2 is an adsorption and desorption isotherm diagram of the silicate high-temperature wave-absorbing composite material in the first experiment;
FIG. 3 is a sum pore size distribution diagram of a silicate high temperature wave-absorbing composite material in experiment one;
FIG. 4 is an infrared spectrum of a silicate high-temperature wave-absorbing composite material in experiment I;
FIG. 5 is a wave-absorbing performance diagram of a silicate high-temperature wave-absorbing composite material in the first experiment;
FIG. 6 is a wave-absorbing performance diagram of the silicate high-temperature wave-absorbing composite material in the first experiment;
FIG. 7 is a wave-absorbing performance diagram of a silicate high-temperature wave-absorbing composite material in experiment two;
FIG. 8 is a wave-absorbing performance diagram of a silicate high-temperature wave-absorbing composite material in experiment II;
FIG. 9 is a wave-absorbing performance diagram of a silicate high-temperature wave-absorbing composite material in experiment III;
FIG. 10 is a wave-absorbing performance diagram of the silicate high-temperature wave-absorbing composite material in experiment III.
Detailed Description
The technical solution of the present invention is not limited to the following specific embodiments, but includes any combination of the specific embodiments.
The first embodiment is as follows: the preparation method of the silicate high-temperature wave-absorbing composite material is carried out according to the following steps:
SiO 22Synthesis of aerogel:
a. mixing a silicon source, an alcohol solvent, N-dimethylformamide and hydrochloric acid according to a molar ratio of (1-5) to 1: 1, then hydrolyzing at 90-100 ℃, and cooling to room temperature after hydrolysis is completed;
b. dropwise adding alkali liquor and stirring for 30-60 minutes to perform polycondensation reaction, wherein the volume ratio of the alkali liquor to the hydrochloric acid is 1-2: 1;
c. transferring the solution in the step b into a mold, sealing, and then putting into an oven with the temperature of 35-50 ℃ for aging for 6-12 hours;
d. soaking the gel in an alcohol solution for 15 hours, and then soaking the gel in a mixed solution of a silicon source solution and the alcohol solution for 24 hours to obtain wet gel;
e. soaking the wet gel in ethanol in an oven at 50 deg.C for 6-12 hr to remove water and silicon source, replacing ethanol with n-hexane, adding modifying solution at molar ratio of 1-2: 1, and sealing to obtain gel;
second, high temperature synthesis of SiO2-ferrite composite material:
f. mixing a silane coupling agent, soluble salt for preparing ferrite, the gel obtained in the step e, an alcohol solvent and deionized water, stirring for 1-2 hours, and ultrasonically dispersing for 30-60 minutes to obtain a mixed solution, wherein the volume percentage concentration of the silane coupling agent in the mixed solution is 0.25-0.5%;
the molar ratio of the gel obtained in the step e to soluble salt for preparing ferrite is 1: 1-2;
the ratio of the gel obtained in the step e to the alcohol solvent is 1g to (40-60) mL;
the ratio of the gel obtained in the step e to the deionized water is 1g to (40-60) mL;
g. transferring the mixed solution obtained in the step f into a high-temperature reaction kettle, heating to 80-120 ℃ at the speed of 2-4 ℃/min, preserving heat for 4-6 h, after the reaction is finished, exchanging and centrifugally cleaning with water and an alcohol solution, washing wet gel with n-hexane, and drying in vacuum to obtain the composite aerogel;
h. under the condition of air or nitrogen, the composite aerogel is placed in a 350-450 ℃ tubular furnace to be roasted for 2-4 h, and then is cooled to room temperature, so that the SiC-ferrite/carbonaceous material high-temperature wave-absorbing composite material is obtained;
the soluble salt for preparing the ferrite in the second step is ferric salt, cobalt salt or nickel salt;
the nickel salt is one or more of nickel chloride hexahydrate, nickel sulfate hexahydrate and nickel nitrate hexahydrate;
the ferric salt is one or more of ferric chloride hexahydrate, ferrous sulfate heptahydrate and ferric nitrate nonahydrate;
the cobalt salt is one or more of cobalt chloride hexahydrate, cobalt sulfate heptahydrate and cobalt nitrate hexahydrate;
the alcohol solvent in the step two f is one or more of ethanol, methanol, propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, cyclobutanol, cyclohexanol, cyclopentanol, isobutanol and isoamylol.
When the nickel salt described in the present embodiment is a composition, the ratio of the components is arbitrary.
When the iron salt described in the present embodiment is a composition, the ratio of the components is arbitrary.
When the cobalt salt described in the present embodiment is a composition, the ratio of the components is arbitrary.
When the alcohol solvent is a composition in the present embodiment, the ratio of the components is arbitrary.
The second embodiment is as follows: this embodiment differs from the embodiment in that in step one a the silicon source is methyl orthosilicate, ethyl orthosilicate, Tetramethoxysilane (TMOS), Tetraethoxysilane (TEOS), Polyethoxydisiloxane (PEDS) or methyltrimethoxysilane (MTMS). The rest is the same as the first embodiment.
The third concrete implementation mode: the difference between the first embodiment and the second embodiment is that the alcohol solvent in the first step a is one or more of ethanol, methanol, propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, cyclobutanol, cyclohexanol, cyclopentanol, isobutanol, and isoamyl alcohol. The others are the same as in the first or second embodiment.
When the alcohol solvent is a composition in the present embodiment, the ratio of the components is arbitrary.
The fourth concrete implementation mode: the difference between this embodiment and one of the first to third embodiments is that the alkali solution in the first step b is an aqueous solution of ammonia, sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, disodium hydrogen phosphate, sodium citrate or potassium citrate. The rest is the same as one of the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is that the alcohol solution mixture in the step (d) is an aqueous solution of two or more of ethanol, methanol, propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, cyclobutanol, cyclohexanol, cyclopentanol, isobutanol, and isoamyl alcohol. The rest is the same as one of the first to fourth embodiments.
When the alcohol solution mixture solution described in the present embodiment is a composition, the ratio of the components is arbitrary.
The sixth specific implementation mode: the present embodiment is different from the first to fifth embodiments in that the molar ratio of the silicon source solution to the alcohol solution mixture in the silicon source solution and the alcohol solution mixture in the step one d is 1-3: 1. The rest is the same as one of the first to fifth embodiments.
The seventh embodiment: this embodiment is different from one of the first to sixth embodiments in that the silicon source solution in the first step is an aqueous solution of silicon source of methyl orthosilicate, ethyl orthosilicate, Tetramethoxysilane (TMOS), Tetraethoxysilane (TEOS), Polyethoxydisiloxane (PEDS) or methyltrimethoxysilane (MTMS). The rest is the same as one of the first to sixth embodiments.
The specific implementation mode is eight: the difference between this embodiment and one of the first to seventh embodiments is that the modification solution in the first step e is Hexamethyldisilazane (HMDZ) or Trimethylchlorosilane (TMCS). The rest is the same as one of the first to seventh embodiments.
The specific implementation method nine: this embodiment is different from the first to eighth embodiments in that the silane coupling agent in the second step f is KH-550, KH-540, KH-560, KH-792, or KH-6020. The rest is the same as the first to eighth embodiments.
The detailed implementation mode is ten: the difference between the present embodiment and one of the first to ninth embodiments is that the temperature of vacuum drying in the second step is 60-80 ℃ and the time is 12-24 h. The rest is the same as one of the first to ninth embodiments.
The following experiments are adopted to verify the effect of the invention:
experiment one:
the preparation method of the silicate high-temperature wave-absorbing composite material comprises the following steps:
SiO 22Synthesis of aerogel:
a. mixing a silicon source, an ethanol solvent, N-dimethylformamide and hydrochloric acid according to a molar ratio of 1: 1, then hydrolyzing at 90 ℃, and cooling to room temperature after hydrolysis is completed;
b. dropping alkali liquor and stirring for 30 minutes to carry out polycondensation reaction, wherein the volume ratio of the alkali liquor to the hydrochloric acid is 1: 1;
c. b, transferring the solution in the step b into a mold, sealing, and then putting into a drying oven at the temperature of 35 ℃ for aging for 12 hours;
d. soaking the gel in an alcohol solution mixed solution for 15 hours, and then soaking the gel in a silicon source solution and the alcohol solution mixed solution for 24 hours to obtain wet gel;
e. soaking the wet gel in ethanol in a 50 ℃ oven for 12 hours, removing water and a silicon source, replacing the ethanol with n-hexane, adding a modifying solution, carrying out surface modification on the gel with the molar ratio of the modifying solution to the silicon source being 2: 1, directly pouring the modifying agent into a conical flask containing the silicon source, and sealing;
second, high temperature synthesis of SiO2-ferrite composite material:
f. mixing a silane coupling agent, soluble salt for preparing ferrite, the gel obtained in the step e, an alcohol solvent and deionized water, stirring for 1h, and performing ultrasonic dispersion for 30min to obtain a mixed solution;
the mol ratio of the gel obtained in the step e to the soluble salt for preparing the ferrite is 1: 1;
the volume percentage concentration of the silane coupling agent in the mixed solution is 0.25 percent;
the ratio of the mass of the aerogel to the volume of the alcohol solvent is 1 g: 40 mL;
the ratio of the mass of aerogel to the volume of deionized water was 1 g: 40 mL;
g. transferring the mixed solution into a high-temperature reaction kettle, heating to 80 ℃ at the speed of 2 ℃/min, preserving heat for 4 hours, after the reaction is finished, exchanging water and an alcohol solution for centrifugal cleaning, washing wet gel with n-hexane, and drying in vacuum to obtain the composite aerogel;
h. and under the condition of air or nitrogen, roasting the composite aerogel in a 350 ℃ tubular furnace for 2 hours, and cooling to room temperature to obtain the SiC-ferrite/carbonaceous material high-temperature wave-absorbing composite material.
The silane coupling agent in the second step f is KH-550.
And the soluble salt for preparing the ferrite in the second step is nickel chloride hexahydrate.
The alcohol solvent in the second step f is ethanol.
In step one a, the silicon source is Tetraethoxysilane (TEOS).
In the step one a, the alcohol solvent is benzyl alcohol.
In the step one b, the alkali liquor is a disodium hydrogen phosphate aqueous solution.
In the step one d, the alcohol solution mixed solution is an aqueous solution of tert-butyl alcohol and benzyl alcohol, and the tert-butyl alcohol and the benzyl alcohol are in any ratio.
In the step one d, the molar ratio of the silicon source solution to the alcohol solution mixed solution in the silicon source solution and the alcohol solution mixed solution is 1: 1.
In the step one d, the silicon source solution is a silicon source Tetraethoxysilane (TEOS) aqueous solution.
In the first step e, the modified solution is Hexamethyldisilazane (HMDZ).
The silane coupling agent in the second step f is KH-540.
In the second step, the temperature of vacuum drying is 60 ℃ and the time is 12 h.
Experiment two:
the preparation method of the silicate high-temperature wave-absorbing composite material comprises the following steps:
SiO 22Synthesis of aerogel:
a. mixing a silicon source, an alcohol solvent, N-dimethylformamide and hydrochloric acid according to the molar ratio of 2: 1, then hydrolyzing at 93 ℃, and cooling to room temperature after the hydrolysis is finished;
b. dropping alkali liquor and stirring for 40 minutes to carry out polycondensation reaction, wherein the volume ratio of the alkali liquor to the hydrochloric acid is 2: 1;
c. transferring the solution in the step b into a mold, sealing, and then putting into a drying oven at 40 ℃ for aging for 8 hours;
d. soaking the gel in an alcohol solution for 15 hours, and then soaking the gel in a mixed solution of a silicon source solution and the alcohol solution for 24 hours to obtain wet gel;
e. soaking the wet gel in ethanol in a 50 ℃ oven for 8 hours to remove water and a silicon source, replacing the ethanol with n-hexane, adding a modification solution, wherein the molar ratio of the modification solution to the silicon source is 2: 1, and sealing to obtain gel;
second, high temperature synthesis of SiO2-ferrite composite material:
f. mixing a silane coupling agent, soluble salt for preparing ferrite, the gel obtained in the step e, an alcohol solvent and deionized water, stirring for 2 hours, and performing ultrasonic dispersion for 40min to obtain a mixed solution, wherein the volume percentage concentration of the silane coupling agent in the mixed solution is 0.3%;
the mol ratio of the gel obtained in the step e to the soluble salt for preparing the ferrite is 1: 2;
the ratio of the gel obtained in the step e to the alcohol solvent is 1g to 50 mL;
the ratio of the gel obtained in the step e to the deionized water is 1g to 50 mL;
g. transferring the mixed solution obtained in the step f into a high-temperature reaction kettle, heating to 90 ℃ at the speed of 3 ℃/min, preserving heat for 5 hours, after the reaction is finished, exchanging water and an alcohol solution for centrifugal cleaning, washing wet gel with n-hexane, and drying in vacuum to obtain the composite aerogel;
h. under the condition of air or nitrogen, the composite aerogel is put into a 380 ℃ tubular furnace to be roasted for 3h and then cooled to room temperature, so as to obtain the SiC-ferrite/carbonaceous material high-temperature wave-absorbing composite material;
the soluble salt for preparing ferrite in the second step is ferrous sulfate heptahydrate.
The alcohol solvent in the second step f is isoamyl alcohol.
In step one a the silicon source is Tetramethoxysilane (TMOS).
In the step one a, the alcohol solvent is benzyl alcohol.
In the step one b, the alkali liquor is potassium carbonate aqueous solution.
And d, mixing the alcohol solution mixed solution in the step one with a mixed aqueous solution of benzyl alcohol, cyclobutanol, cyclohexanol and cyclopentanol in any ratio.
In the step one d, the molar ratio of the silicon source solution to the alcohol solution mixed solution in the silicon source solution and the alcohol solution mixed solution is 2: 1.
In the step one d, the silicon source solution is an aqueous solution of polyethoxy disiloxane (PEDS).
In the step one e, the modification liquid is Trimethylchlorosilane (TMCS).
The silane coupling agent in the second step f is KH-792.
And the temperature of vacuum drying in the second step is 70 ℃, and the time is 20 hours.
Experiment three:
the preparation method of the silicate high-temperature wave-absorbing composite material comprises the following steps:
SiO 22Synthesis of aerogel:
a. mixing a silicon source, an alcohol solvent, N-dimethylformamide and hydrochloric acid according to a molar ratio of 5: 1, then hydrolyzing at 100 ℃, and cooling to room temperature after the hydrolysis is finished;
b. dropping alkali liquor and stirring for 60 minutes to carry out polycondensation reaction, wherein the volume ratio of the alkali liquor to the hydrochloric acid is 2: 1;
c. transferring the solution in the step b into a mold, sealing, and then putting into a 50 ℃ oven for aging for 12 hours;
d. soaking the gel in an alcohol solution for 15 hours, and then soaking the gel in a mixed solution of a silicon source solution and the alcohol solution for 24 hours to obtain wet gel;
e. soaking the wet gel in ethanol in a 50 ℃ oven for 12 hours to remove water and a silicon source, replacing the ethanol with n-hexane, adding a modification solution, wherein the molar ratio of the modification solution to the silicon source is 2: 1, and sealing to obtain gel;
second, high temperature synthesis of SiO2-ferrite composite material:
f. mixing a silane coupling agent, soluble salt for preparing ferrite, the gel obtained in the step e, an alcohol solvent and deionized water, stirring for 2 hours, and performing ultrasonic dispersion for 60 minutes to obtain a mixed solution, wherein the volume percentage concentration of the silane coupling agent in the mixed solution is 0.5%;
the mol ratio of the gel obtained in the step e to the soluble salt for preparing the ferrite is 1: 2;
the ratio of the gel obtained in the step e to the alcohol solvent is 1g to 60 mL;
the ratio of the gel obtained in the step e to the deionized water is 1 g: 60 mL;
g. transferring the mixed solution obtained in the step f into a high-temperature reaction kettle, heating to 120 ℃ at the speed of 4 ℃/min, preserving heat for 6 hours, after the reaction is finished, exchanging water and an alcohol solution for centrifugal cleaning, washing wet gel with n-hexane, and drying in vacuum to obtain the composite aerogel;
h. under the condition of air or nitrogen, the composite aerogel is put into a 450 ℃ tubular furnace to be roasted for 4 hours and then cooled to room temperature, so as to obtain the SiC-ferrite/carbonaceous material high-temperature wave-absorbing composite material;
the soluble salt for preparing the ferrite in the second step is a composition of cobalt chloride hexahydrate, cobalt sulfate heptahydrate and cobalt nitrate hexahydrate, and the ratio of the cobalt chloride hexahydrate, the cobalt sulfate heptahydrate and the cobalt nitrate hexahydrate is any ratio;
the alcohol solvent in the second step f is a mixture of cyclopentanol, isobutanol and isoamylol, and the ratio of the components in the mixture is arbitrary.
In step one a the silicon source is methyltrimethoxysilane (MTMS).
In the step one a, the alcohol solvent is a mixture of ethanol and n-butanol, tert-butanol, benzyl alcohol, cyclobutanol and cyclohexanol, and the components in the mixture are in any ratio.
In the step one b, the alkali liquor is a potassium citrate aqueous solution.
And d, mixing the alcohol solution mixed solution in the step one with mixed water solution of cyclobutanol, cyclohexanol, cyclopentanol, isobutanol and isoamylol, wherein the ratio of the cyclobutanol to the cyclohexanol to the isobutanol is any.
In the step one d, the molar ratio of the silicon source solution to the alcohol solution mixed solution in the silicon source solution and the alcohol solution mixed solution is 3: 1.
In the step one d, the silicon source solution is an aqueous solution of methyltrimethoxysilane (MTMS).
In the step one e, the modifying solution is hexamethyldisilazane.
And the silane coupling agent in the second step f is KH-6020.
And the temperature of vacuum drying in the second step g is 80 ℃, and the time is 24 hours.

Claims (10)

1. The preparation method of the silicate high-temperature wave-absorbing composite material is characterized by comprising the following steps of:
SiO 22Synthesis of aerogel:
a. mixing a silicon source, an alcohol solvent, N-dimethylformamide and hydrochloric acid according to a molar ratio of (1-5) to 1: 1, then hydrolyzing at 90-100 ℃, and cooling to room temperature after hydrolysis is completed;
b. dropwise adding alkali liquor and stirring for 30-60 minutes to perform polycondensation reaction, wherein the volume ratio of the alkali liquor to the hydrochloric acid is 1-2: 1;
c. transferring the solution in the step b into a mold, sealing, and then putting into an oven with the temperature of 35-50 ℃ for aging for 6-12 hours;
d. soaking the gel in an alcohol solution for 15 hours, and then soaking the gel in a mixed solution of a silicon source solution and the alcohol solution for 24 hours to obtain wet gel;
e. soaking the wet gel in ethanol in an oven at 50 deg.C for 6-12 hr to remove water and silicon source, replacing ethanol with n-hexane, adding modifying solution at molar ratio of 1-2: 1, and sealing to obtain gel;
second, high temperature synthesis of SiO2-ferrite composite material:
f. mixing a silane coupling agent, soluble salt for preparing ferrite, the gel obtained in the step e, an alcohol solvent and deionized water, stirring for 1-2 hours, and ultrasonically dispersing for 30-60 minutes to obtain a mixed solution, wherein the volume percentage concentration of the silane coupling agent in the mixed solution is 0.25-0.5%;
the molar ratio of the gel obtained in the step e to soluble salt for preparing ferrite is 1: 1-2;
the ratio of the gel obtained in the step e to the alcohol solvent is 1g to (40-60) mL;
the ratio of the gel obtained in the step e to the deionized water is 1g to (40-60) mL;
g. transferring the mixed solution obtained in the step f into a high-temperature reaction kettle, heating to 80-120 ℃ at the speed of 2-4 ℃/min, preserving heat for 4-6 h, after the reaction is finished, exchanging and centrifugally cleaning with water and an alcohol solution, washing wet gel with n-hexane, and drying in vacuum to obtain the composite aerogel;
h. under the condition of air or nitrogen, the composite aerogel is placed in a 350-450 ℃ tubular furnace to be roasted for 2-4 h, and then is cooled to room temperature, so that the SiC-ferrite/carbonaceous material high-temperature wave-absorbing composite material is obtained;
the soluble salt for preparing the ferrite in the second step is ferric salt, cobalt salt or nickel salt;
the nickel salt is one or more of nickel chloride hexahydrate, nickel sulfate hexahydrate and nickel nitrate hexahydrate;
the ferric salt is one or more of ferric chloride hexahydrate, ferrous sulfate heptahydrate and ferric nitrate nonahydrate;
the cobalt salt is one or more of cobalt chloride hexahydrate, cobalt sulfate heptahydrate and cobalt nitrate hexahydrate;
the alcohol solvent in the step two f is one or more of ethanol, methanol, propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, cyclobutanol, cyclohexanol, cyclopentanol, isobutanol and isoamylol.
2. The method for preparing the silicate high-temperature wave-absorbing composite material according to claim 1, wherein the silicon source in the step a is methyl orthosilicate, ethyl orthosilicate, tetramethoxysilane, tetraethoxysilane, polyethoxydisiloxane or methyltrimethoxysilane.
3. The preparation method of the silicate high-temperature wave-absorbing composite material according to claim 1, wherein the alcohol solvent in the step a is one or more of ethanol, methanol, propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, cyclobutanol, cyclohexanol, cyclopentanol, isobutanol, and isoamyl alcohol.
4. The method for preparing the silicate high-temperature wave-absorbing composite material according to claim 1, wherein the alkali solution in the step (b) is an aqueous solution of ammonia, sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, disodium hydrogen phosphate, sodium citrate or potassium citrate.
5. The method for preparing the silicate high-temperature wave-absorbing composite material according to claim 1, wherein the alcohol solution mixed solution in the step (d) is an aqueous solution of two or more of ethanol, methanol, propanol, isopropanol, n-butanol, t-butanol, benzyl alcohol, cyclobutanol, cyclohexanol, cyclopentanol, isobutanol, and isoamyl alcohol.
6. The method for preparing the silicate high-temperature wave-absorbing composite material according to claim 1, wherein the molar ratio of the silicon source solution to the alcohol solution mixed solution in the silicon source solution and the alcohol solution mixed solution in the step (d) is 1-3: 1.
7. The method for preparing the silicate high-temperature wave-absorbing composite material according to claim 1, wherein the silicon source solution in the step (d) is an aqueous solution of silicon source of methyl orthosilicate, ethyl orthosilicate, tetramethoxysilane, tetraethoxysilane, polyethoxydisiloxane or methyltrimethoxysilane.
8. The method for preparing the silicate high-temperature wave-absorbing composite material according to claim 1, wherein the modifying solution in the step (e) is hexamethyldisilazane or trimethylchlorosilane.
9. The method for preparing the silicate high-temperature wave-absorbing composite material according to claim 1, wherein the silane coupling agent in the second step f is KH-550, KH-540, KH-560, KH-792 or KH-6020.
10. The preparation method of the silicate high-temperature wave-absorbing composite material according to claim 1, wherein the temperature of vacuum drying in the second step is 60-80 ℃ and the time is 12-24 h.
CN201911055121.5A 2019-10-31 2019-10-31 Preparation method of silicate high-temperature wave-absorbing composite material Pending CN110760291A (en)

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