A method for preparing ZrSiO4 aerogel by sol-gel combined supercritical drying

Abstract

The application discloses a method for preparing ZrSiO4 aerogel by sol-gel combined supercritical drying, and the wet gel is prepared by using a silicon source, a zirconium source and a crosslinking agent as raw materials, then the low-density and high-porosity dry gel is obtained by CO2 supercritical drying, and then the control of the gel component and structure is realized by controlling the heat treatment process, so that the ZrSiO4 aerogel with low density, high porosity, excellent high-temperature resistance and good thermal stability is obtained. Through the control of the component, the gel process and the heat treatment process, the controllable preparation and performance regulation of the ZrSiO4 aerogel are realized.

Description

TECHNICAL FIELD

[0001] The technical scheme of the present application provides a method for preparing ZrSiO4 aerogel by sol-gel combined with supercritical drying, and belongs to the field of heat insulation material preparation. BACKGROUND

[0002] For applications in extreme thermal environments, such as thermal protection structures of spacecraft and military vehicles, heat insulation structures of industrial high-temperature equipment, etc., the material needs to meet the requirements of light weight, ultra-low thermal conductivity, high thermal stability, excellent mechanical properties, etc. at the same time. Although traditional ceramic aerogels have extremely low thermal conductivity due to their nano-porous structure, their inherent brittleness leads to low compression strain, making them difficult to withstand mechanical impact or thermal stress and prone to cracking failure. At high temperatures, they are prone to structure collapse due to crystallization and powdering, losing the heat insulation function. Existing reinforcement methods, such as fiber doping, can improve the mechanical resilience, but often lead to an increase in thermal conductivity. Traditional preparation processes such as precipitation and hydrothermal method have poor structure controllability and single fiber orientation, making it difficult to mass-produce complex three-dimensional components, limiting the application of traditional ceramic aerogels in heat insulation of special-shaped parts. Therefore, it is of great significance to develop new ceramic aerogels with ultra-light, high-elastic, heat insulation, and excellent high-temperature stability, and to realize their structure design and performance control for large-scale production to meet the needs of efficient thermal protection in extreme environments.

[0003] Aerogel is a low-density porous solid material composed of nanoparticles or polymer molecules aggregated with each other, having high porosity and large internal surface area. The preparation method of aerogel is usually to first prepare a gel through chemical reaction, and then to obtain aerogel through drying. Sol-gel method is a common method for preparing aerogel, but the pores of wet gel are prone to collapse during drying due to the action of capillary force, leading to the fragmentation of dry gel. However, supercritical drying can avoid the action of capillary force and obtain aerogel with complete structure. Organic solvent supercritical drying reaches and maintains the supercritical state of organic solvent without crossing the liquid-gas phase boundary, and then reduces the pressure to ambient pressure at constant temperature to achieve the purpose of drying, but the process of reaching the supercritical state may damage the structure of the gel. The critical conditions of CO2 (31 ℃ and 74 bar) are more moderate than those of organic solvents such as ethanol (241.3 ℃ and 61 bar) and acetone (235 ℃ and 47 bar), causing less change in gel structure. CO2 supercritical drying combined with sol-gel process is a common method for preparing aerogel.

[0004] ZrSiO4 is a high-temperature structural ceramic material with a melting point of more than 2400 ℃, excellent chemical stability, low thermal expansion coefficient and low thermal conductivity. As an advanced ceramic material with high-temperature stability and good mechanical properties, its high melting point and oxidation resistance make it possible to realize the realization of aerogel materials in extreme environments. Zirconium silicate ceramic is prepared into aerogel, which is expected to obtain aerogel materials with low density, high elasticity, high flexibility, high thermal stability and high thermal insulation, etc., to overcome the shortcomings of traditional ceramic aerogel such as high brittleness, easy pulverization and poor high-temperature stability, so as to better meet the needs of high-efficiency thermal protection in extreme environments.

[0005] At present, ZrSiO4 aerogel cannot be applied in the fields of aerospace thermal protection and high-temperature thermal insulation due to its low use temperature (below 1200 ℃) and poor long-term thermal stability. In previous studies, sol-gel method or electrospinning method was mostly used, and then combined with medium-low temperature heat treatment process or non-heat treatment process to prepare ZrSiO4 aerogel. In order to retain the performance of high porosity and high specific surface area of aerogel, the high-temperature resistance of aerogel is usually sacrificed. The phase composition of ZrSiO4 aerogel prepared in previous studies is mainly SiO2, ZrO2 and a small amount of ZrSiO4, which will produce crystallization, sintering and other phenomena at extremely high temperature, resulting in performance degradation. Therefore, it is of great significance to prepare ZrSiO4 aerogel with high porosity, low density, high-temperature resistance and good long-term thermal stability for its application in the fields of aerospace thermal protection and high-temperature thermal insulation. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of high-temperature-resistant ZrSiO4 aerogel, which solves the problems of low use temperature and poor long-term thermal stability of existing ZrSiO4 aerogel. In previous studies, medium-low temperature sintering process leads to low ZrSiO4 content in ZrSiO4 aerogel and low limit use temperature. The present application adopts high-temperature sintering process, and the phase composition of the prepared aerogel is mainly ZrSiO4, and the use temperature can reach more than 1500 ℃. The ZrSiO4 aerogel prepared by the present application significantly improves the thermal stability, high-temperature resistance and ablation resistance of the material while reducing the cost. It provides a new idea and scheme for the application of ZrSiO4 aerogel in the fields of thermal protection and high-temperature thermal insulation.

[0007] The technical scheme of the present application adopts sol-gel method combined with supercritical drying process to prepare ZrSiO4 aerogel. Zirconium oxy salt or alkoxide is used as zirconium source; organic silane precursor or inorganic silicon compound is used as silicon source; acid, base or organic compound is used as crosslinking agent; the zirconium source, silicon source and crosslinking agent are mixed and gelled at a certain temperature, and then the gel is subjected to CO2 supercritical drying to obtain dry gel, and the dry gel is converted into ZrSiO4 aerogel through heat treatment.

[0008] Compared with the prior art, the technical scheme of the present application solves the problems of the prior method that it is difficult to prepare ZrSiO4 aerogel, the use temperature is low (below 1200 ℃) and the long-term thermal stability is poor, by selecting appropriate silicon source, zirconium source and crosslinking agent, and through the design of raw material components, gel process control, supercritical drying and the design of heat treatment conditions, and high porosity, low density, good high temperature resistance and good long-term thermal stability of ZrSiO4 aerogel are obtained. The implementation of the technology provides a new idea and scheme for the research and development of high-temperature insulation ZrSiO4 aerogel material, and can further improve the use temperature range of high-temperature aerogel material.

[0009] The present application is a method for preparing ZrSiO4 aerogel by sol-gel combined with supercritical drying, which is carried out according to the following steps:

[0010] (1) Dissolve the crosslinking agent in a mixed solution of anhydrous ethanol and deionized water, and stir to mix uniformly; the crosslinking agent is one or more of malic acid, tartaric acid, polymaleic acid, polyacrylic acid, hexamethylenetetramine, formamide, polyethyleneimine, propylene oxide, polyvinyl alcohol, and sodium carboxymethyl cellulose; the volume ratio of anhydrous ethanol to deionized water is 0.01:1 to 1:0.01;

[0011] (2) Add the silicon source and zirconium source to the mixed solution containing the crosslinking agent, and stir to form a precursor solution; the temperature range for stirring the raw materials is 1-80 ℃, and the stirring time is 0.1-24 h; the silicon source is one or more of tetraethyl orthosilicate, dimethyldiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, γ-aminopropyltriethoxysilane, silica sol and sodium silicate; the zirconium source is one or more of zirconium oxychloride, zirconyl nitrate, zirconium n-butylate, zirconium acetate, zirconium sulfate and zirconium isopropylate; the concentration ratio of the silicon source, the zirconium source and the crosslinking agent in the raw materials is 1.0-2.0:1.0-2.0:0.01-4.0;

[0012] (3) Gel the precursor solution in an oven, the gel temperature is 30-90 ℃, and the gel time is 0.5-72 h; the obtained wet gel is soaked in ethanol for 24-72 h;

[0013] (4) Put the obtained wet gel into a CO2 supercritical drying reaction kettle, maintain the temperature in the reaction kettle at 4 ℃, and replace with liquid CO2 for 0.5-72 h; increase the temperature in the reaction kettle to make CO2 reach the supercritical state, maintain for 0.1-24 h, then depressurize and take out the dried gel;

[0014] (5) the dried gel is placed into a muffle furnace for high-temperature heat treatment, the heat treatment temperature is 1000-1600 DEG C, the heating rate is 1-5 DEG C / min, the holding time is 0.5-12 h, and the cooling rate is 1-5 DEG C / min, to obtain ZrSiO4 aerogel.

[0015] The advantages of the present application relative to the prior art are as follows:

[0016] First, a suitable silicon source and zirconium source are co-hydrolyzed at low temperature, and the stability of the sol is dynamically regulated by a crosslinking agent to form a uniform precursor network, which realizes uniform mixing of the silicon source and zirconium source, is conducive to uniform subsequent reaction and avoids the generation of impurity phases.

[0017] Second, under CO2 supercritical conditions, the gel maintains high porosity, low density and an intact gel network after the drying process; after 1000-1600 DEG C heat treatment, ZrO2 and SiO2 are efficiently reacted to generate ZrSiO4, and ZrSiO4 aerogel with high porosity, low density, good high-temperature performance and good long-term thermal stability is obtained.

[0018] Third, the present application solves the problems of low ZrSiO4 content, low use temperature and poor long-term thermal stability in the preparation of ZrSiO4 aerogel. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A physical map of ZrSiO4 aerogel prepared in Example 1;

[0020] Figure 2 An XRD map of ZrSiO4 aerogel prepared in Example 1;

[0021] Figure 3 A physical map of ZrSiO4 aerogel prepared in Example 2;

[0022] Figure 4 An XRD map of ZrSiO4 aerogel prepared in Example 2;

[0023] Figure 5 An SEM map of ZrSiO4 aerogel prepared in Example 3. DETAILED DESCRIPTION

[0024] The present application is further described below in conjunction with examples. However, the scope of the present application is not limited to the following examples. Those skilled in the art can understand that various changes and modifications can be made to the present application without departing from the spirit and scope of the present application.

[0025] Unless otherwise specified, the instruments, reagents, and materials used in the following embodiments are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods used in the following embodiments are all conventional experimental methods and detection methods already available in the prior art.

[0026] Example 1

[0027] A method for preparing ZrSiO4 aerogel using a sol-gel combination and supercritical drying includes the following steps:

[0028] (1) First, dissolve 0.2 g of malic acid in a mixed solution of anhydrous ethanol and deionized water and stir evenly on a magnetic stirrer; the volume ratio of anhydrous ethanol to deionized water is 1:1.

[0029] (2) Tetraethyl orthosilicate and zirconium oxychloride were added to a mixed solution containing a crosslinking agent and stirred until homogeneous to form a precursor solution; the solution was placed in a 20 ℃ water bath and stirred for 20 h; the tetraethyl orthosilicate, zirconium oxychloride and malic acid were in a concentration ratio of 1:1:0.1;

[0030] (3) Place the mixed solution in an oven at 20 °C, gel for 60 h, and then soak it in ethanol for 60 h;

[0031] (4) The obtained wet gel was placed in a CO2 supercritical drying reactor and the temperature inside the reactor was maintained at 4 ℃. Liquid CO2 was used to replace the gel for 60 h. The temperature inside the reactor was raised to 40 ℃ and held for 2 h after reaching the supercritical state. Then the pressure was released and the dried gel was taken out.

[0032] (5) The supercritical dried sample was placed in a muffle furnace and heated to 1000 °C at a rate of 1 °C / min in an air atmosphere, and held at that temperature for 12 h. After cooling to room temperature, a ZrSiO4 aerogel with high porosity, low density, good high temperature resistance and good long-term thermal stability was obtained. The physical image and XRD pattern of the ZrSiO4 aerogel prepared in this example are attached. Figure 1 and 2 As shown, the aerogel has a high ZrSiO4 phase content; the ZrSiO4 aerogel prepared in this example has a porosity of 96.8% and a density of 0.1459 g / cm³. 3 The pore volume is 1.68 cm³. 3 / g, specific surface area 90.6 m² 2 / g, compressive strength 2.75 MPa, compressive strain 7.0%, thermal conductivity 0.039 W·m -1 K -1; After 2 hours of high-temperature calcination at 1500 ℃, slight agglomeration occurred, the pore structure was basically maintained, and the ZrSiO4 aerogel did not decompose; after the one side of the ZrSiO4 aerogel was heated by a butane torch flame (> 1300 ℃) for 5 minutes, the temperature on the other side of the ZrSiO4 aerogel was stably below 50 ℃, indicating that the ZrSiO4 aerogel prepared in Example 1 has excellent heat insulation performance; the sample was first rapidly heated to 1000 ℃, and then rapidly cooled to ambient temperature (room temperature), and the temperature change rate was as high as 200 ℃ / min; after 30 cycles of high-temperature thermal shock, the overall structure of the aerogel remained the original form, indicating that the ZrSiO4 aerogel prepared in Example 1 has excellent thermal shock resistance.

[0033] Example 2

[0034] A method for preparing a ZrSiO4 aerogel by sol-gel combined with supercritical drying, comprising the following steps:

[0035] (1) First, 0.1 g of tartaric acid was dissolved in a mixed solution of anhydrous ethanol and deionized water, and uniformly stirred on a magnetic stirrer; the volume ratio of anhydrous ethanol to deionized water was 0.01:1;

[0036] (2) Dimethyldiethoxysilane and zirconyl nitrate were added to the mixed solution containing the crosslinking agent to form a precursor solution; the solution was placed in a 30 ℃ water bath for stirring for 24 h; the concentration ratio of dimethyldiethoxysilane, zirconyl nitrate and tartaric acid was 1:1:0.01;

[0037] (3) The mixed solution was placed in a 30 ℃ oven, and the gel was soaked in ethanol for 70 h after 70 h of gelation;

[0038] (4) The obtained wet gel was placed in a CO2 supercritical drying reaction kettle, the temperature in the reaction kettle was maintained at 4 ℃, and liquid CO2 was used for replacement for 60 h; the temperature in the reaction kettle was increased to 40 ℃, and when the supercritical state was reached, the temperature was maintained for 12 h, then the pressure was released and the dried gel was taken out;

[0039] (5) The sample after supercritical drying was placed in a muffle furnace, and heated to 1100 ℃ at a rate of 2 ℃ / min in an air atmosphere, and maintained for 6 h; after cooling to room temperature, a ZrSiO4 aerogel with high porosity, low density, good high-temperature resistance and long-term thermal stability was obtained, and the actual picture and XRD pattern of the ZrSiO4 aerogel prepared in this example are shown in Figs. 1 and 2, respectively, and the ZrSiO4 phase content in the aerogel is high; the porosity of the ZrSiO4 aerogel prepared in this example is 97.8%, the density is 0.1003 g / cm Figure 3 and 4 3 , and the pore volume is 1.72 cm​3 / g, specific surface area 87.2 m 2 / g, compressive strength 2.98 MPa, compressive strain 6.7%, thermal conductivity 0.033 W·m -1 K -1 ; after 2 hours of high-temperature calcination at 1500 ℃, slight agglomeration occurred, the pore structure was basically maintained, and the ZrSiO4 aerogel did not decompose; after the one side of the ZrSiO4 aerogel was heated by a butane torch flame (>1300 ℃) for 5 minutes, the temperature on the other side of the ZrSiO4 aerogel was stably below 60 ℃, indicating that the ZrSiO4 aerogel prepared in Example 2 had excellent heat insulation performance; the sample was rapidly heated to 1100 ℃ and then cooled to ambient temperature (room temperature), and the temperature change rate was as high as 220 ℃ / min; after 35 cycles of high-temperature thermal shock, the overall structure of the aerogel remained the original form, indicating that the ZrSiO4 aerogel prepared in Example 2 had excellent thermal shock resistance.

[0040] Example 3

[0041] A method for preparing a ZrSiO4 aerogel by sol-gel combined with supercritical drying, comprising the following steps:

[0042] (1) First, 0.3 g of polymaleic acid was dissolved in a mixed solution of anhydrous ethanol and deionized water, and uniformly stirred on a magnetic stirrer; the volume ratio of anhydrous ethanol to deionized water was 0.5:1;

[0043] (2) Methyltrimethoxysilane and zirconium n-butoxide were added to the mixed solution containing the crosslinking agent to form a precursor solution; the solution was placed in a 40 ℃ water bath for stirring for 12 h; the concentration ratio of methyltrimethoxysilane, zirconium n-butoxide and polymaleic acid was 1:1:0.5;

[0044] (3) The mixed solution was placed in a 40 ℃ oven, and after 72 h of gelation, it was soaked in ethanol for 72 h;

[0045] (4) The obtained wet gel was placed in a CO2 supercritical drying reaction kettle, the temperature in the reaction kettle was maintained at 4 ℃, and liquid CO2 was used to replace for 60 h; the temperature in the reaction kettle was increased to 40 ℃, and when the supercritical state was reached, it was maintained for 18 h, then the pressure was released and the dried gel was taken out;

[0046] (5) The sample after supercritical drying was placed in a muffle furnace, and heated to 1300 ℃ at a rate of 3 ℃ / min in an air atmosphere, and maintained for 12 h; cooling to room temperature to obtain a ZrSiO4 aerogel with high porosity, low density, good high-temperature resistance and long-term thermal stability, and high ZrSiO4 phase content in the aerogel; the SEM images of the ZrSiO4 aerogel prepared in this example are shown in FIGS. 1 and 2.Figure 5 The porosity of the ZrSiO4 aerogel prepared in this embodiment is 96.6%, and the density is 0.1550 g / cm 3 , the pore volume is 1.69 cm 3 / g, the specific surface area is 98.2 m 2 / g, the compressive strength is 2.21 MPa, the compressive strain is 5.9%, and the thermal conductivity is 0.036 W·m -1 K -1 ; after high-temperature calcination at 1500 ℃ for 2 hours, slight agglomeration occurs, the pore structure is basically maintained, and the ZrSiO4 aerogel does not decompose; after the one side of the ZrSiO4 aerogel is heated by a butane torch flame (>1300 ℃) for 5 minutes, the temperature on the other side of the ZrSiO4 aerogel stabilizes below 70 ℃, indicating that the ZrSiO4 aerogel prepared in Example 3 has excellent heat insulation performance; after the sample is first rapidly heated to 1300 ℃ and then cooled to ambient temperature (room temperature) at a temperature change rate of up to 250 ℃ / min, the overall structure of the aerogel maintains the original form after 40 cycles of high-temperature thermal shock, indicating that the ZrSiO4 aerogel prepared in Example 3 has excellent thermal shock resistance.

[0047] Example 4

[0048] A method for preparing a ZrSiO4 aerogel by a sol-gel combined supercritical drying method, comprising the following steps:

[0049] (1) First, 0.1 g of polyacrylic acid is dissolved in a mixed solution of anhydrous ethanol and deionized water, and uniformly stirred on a magnetic stirrer; the volume ratio of anhydrous ethanol to deionized water is 1:0.6;

[0050] (2) Methyltrimethoxysilane and zirconyl nitrate are added to the mixed solution containing the crosslinking agent, and stirred uniformly to form a precursor solution; the solution is placed in a 40 ℃ water bath for stirring for 18 h; the concentration ratio of methyltrimethoxysilane, zirconyl nitrate and polyacrylic acid is 1:1.5:1;

[0051] (3) The mixed solution is placed in a 40 ℃ oven, and after gelation for 24 h, it is soaked in ethanol for 24 h;

[0052] (4) The obtained wet gel is placed in a CO2 supercritical drying reaction kettle, the temperature in the reaction kettle is maintained at 4 ℃, and liquid CO2 is used to replace for 36 h; the temperature in the reaction kettle is increased to 35 ℃, and when the supercritical state is reached, it is maintained for 0.7 h, then the pressure is released and the dried gel is taken out;

[0053] (5) The sample after supercritical drying is placed in a muffle furnace, and heated to 1500 ℃ at a rate of 2 ℃ / min in an air atmosphere, and kept for 3 h; cooled to room temperature to obtain ZrSiO4 aerogel with high porosity, low density, good high-temperature resistance and long-term thermal stability, and high ZrSiO4 phase content in the aerogel; the ZrSiO4 aerogel prepared in this embodiment has a porosity of 96.6%, a density of 0.1550 g / cm 3 , a pore volume of 1.45 cm 3 / g, a specific surface area of 69.3 m 2 / g, a compressive strength of 2.19 MPa, a compressive strain of 7.9%, and a thermal conductivity of 0.042 W·m -1 K -1 ; after 2 h of high-temperature calcination at 1500 ℃, slight agglomeration occurs, the pore structure is basically maintained, and the ZrSiO4 aerogel does not decompose; after the one side of the ZrSiO4 aerogel is heated by a butane torch flame (>1300 ℃) for 5 min, the temperature of the other side of the ZrSiO4 aerogel stabilizes below 65 ℃, indicating that the ZrSiO4 aerogel prepared in Example 4 has excellent heat insulation performance; the sample is first rapidly heated to 1500 ℃, and then cooled to ambient temperature (room temperature) at a temperature change rate of up to 300 ℃ / min; after 45 cycles of high-temperature thermal shock, the overall structure of the aerogel maintains the original form, indicating that the ZrSiO4 aerogel prepared in Example 4 has excellent thermal shock resistance.

[0054] Example 5

[0055] A method for preparing ZrSiO4 aerogel by sol-gel combined with supercritical drying, comprising the following steps:

[0056] (1) First, 0.1 g of hexamethylenetetramine is dissolved in a mixed solution of anhydrous ethanol and deionized water, and uniformly stirred on a magnetic stirrer; the volume ratio of anhydrous ethanol to deionized water is 0.2:1;

[0057] (2) γ-aminopropyltriethoxysilane and zirconium sulfate are added to the mixed solution containing the crosslinking agent, and stirred uniformly to form a precursor solution; the solution is placed in a 80 ℃ water bath for stirring for 0.5 h; the concentration ratio of methyltrimethoxysilane, zirconyl nitrate and polyacrylic acid is 2:1:0.01;

[0058] (3) The mixed solution is placed in a 55 ℃ oven, and after 50 h of gelation, it is soaked in ethanol for 24 h;

[0059] (4) the obtained wet gel is placed into a CO2 supercritical drying reaction kettle, the temperature in the reaction kettle is maintained at 4 ℃, liquid CO2 is used for replacement for 24 h; the temperature in the reaction kettle is increased to 40 ℃, and when the supercritical state is reached, 1 h is maintained, then the pressure is released and the dried gel is taken out;

[0060] (5) the sample after supercritical drying is placed into a muffle furnace, and heated to 1400 ℃ at a rate of 4 ℃ / min under an air atmosphere, and maintained for 3 h; after cooling to room temperature, a ZrSiO4 aerogel with high porosity, low density, good high-temperature resistance and good long-term thermal stability is obtained; the ZrSiO4 aerogel prepared in this embodiment has a porosity of 96.2% and a density of 0.1733 g / cm 3 .

[0061] Example 6

[0062] A method for preparing a ZrSiO4 aerogel by sol-gel combined with supercritical drying, comprising the following steps:

[0063] (1) first, 0.1 g of formamide is dissolved in a mixed solution of anhydrous ethanol and deionized water, and uniformly stirred on a magnetic stirrer; the volume ratio of anhydrous ethanol to deionized water is 0.6:1;

[0064] (2) sodium silicate and zirconium acetate are added to the mixed solution containing the crosslinking agent to form a precursor solution; the solution is placed in a 10 ℃ water bath and stirred for 6 h; the concentration ratio of sodium silicate, zirconium acetate and formamide is 2:2:0.01;

[0065] (3) the mixed solution is placed in a 50 ℃ oven, and the gel is soaked in ethanol for 60 h after 36 h;

[0066] (4) the obtained wet gel is placed into a CO2 supercritical drying reaction kettle, the temperature in the reaction kettle is maintained at 4 ℃, liquid CO2 is used for replacement for 8 h; the temperature in the reaction kettle is increased to 40 ℃, and when the supercritical state is reached, 0.5 h is maintained, then the pressure is released and the dried gel is taken out;

[0067] (5) the sample after supercritical drying is placed into a muffle furnace, and heated to 1600 ℃ at a rate of 2 ℃ / min under an air atmosphere, and maintained for 1 h; after cooling to room temperature, a ZrSiO4 aerogel with high porosity, low density, good high-temperature resistance and good long-term thermal stability is obtained; the ZrSiO4 aerogel prepared in this embodiment has a porosity of 93.8% and a density of 0.2827 g / cm 3 .

[0068] Example 7

[0069] A method for preparing ZrSiO4 aerogel by sol-gel combined with supercritical drying, comprising the following steps:

[0070] (1) First, 0.1 g of polyethyleneimine is dissolved in a mixed solution of anhydrous ethanol and deionized water, and uniformly stirred on a magnetic stirrer; the volume ratio of anhydrous ethanol to deionized water is 1:0.2;

[0071] (2) Silica sol and zirconium oxychloride are added to the mixed solution containing the crosslinking agent, and uniformly stirred to form a precursor solution; the solution is placed in a 50℃ water bath for stirring for 8 hours; the concentration ratio of silica sol, zirconium oxychloride and polyethyleneimine is 1:1:1.5;

[0072] (3) The mixed solution is placed in a 35℃ oven, and after gelation for 12 hours, it is soaked in ethanol for 20 hours;

[0073] (4) The obtained wet gel is placed in a CO2 supercritical drying reaction kettle, the temperature in the reaction kettle is maintained at 4℃, and liquid CO2 is used to replace for 48 hours; the temperature in the reaction kettle is increased to 40℃, and when the supercritical state is reached, it is maintained for 0.5 hours, then the pressure is released and the dried gel is taken out;

[0074] (5) The sample after supercritical drying is placed in a muffle furnace, and heated to 1150℃ at a rate of 3℃ / min in an air atmosphere, and held for 10 hours; after cooling to room temperature, ZrSiO4 aerogel with high porosity, low density, good high-temperature performance and long-term thermal stability is obtained; the porosity of the ZrSiO4 aerogel prepared in this example is 95.5%, and the density is 0.2025 g / cm 3 .

[0075] Example 8

[0076] A method for preparing ZrSiO4 aerogel by sol-gel combined with supercritical drying, comprising the following steps:

[0077] (1) First, 0.1 g of propylene oxide is dissolved in a mixed solution of anhydrous ethanol and deionized water, and uniformly stirred on a magnetic stirrer; the volume ratio of anhydrous ethanol to deionized water is 0.8:1;

[0078] (2) Tetraethyl orthosilicate and zirconium sulfate are added to the mixed solution containing the crosslinking agent, and uniformly stirred to form a precursor solution; the solution is placed in a 45℃ water bath for stirring for 8 hours; the concentration ratio of tetraethyl orthosilicate, zirconium sulfate and propylene oxide is 2:2:4;

[0079] (3) The mixed solution is placed in a 60℃ oven, and after gelation for 24 hours, it is soaked in ethanol for 48 hours;

[0080] (4) the obtained wet gel is placed into a CO2 supercritical drying reaction kettle, the temperature in the reaction kettle is maintained at 4 ℃, liquid CO2 is used for replacement for 72 h; the temperature in the reaction kettle is increased to 40 ℃, and after reaching the supercritical state, 0.5 h is maintained, then pressure is released and the dried gel is taken out;

[0081] (5) the sample after supercritical drying is placed into a muffle furnace, and heated to 1600 ℃ at a rate of 3 ℃ / min under an air atmosphere, and heat preservation is performed for 0.5 h; after cooling to room temperature, ZrSiO4 aerogel with high porosity, low density, good high-temperature resistance and good long-term thermal stability is obtained; the ZrSiO4 aerogel prepared in this embodiment has a porosity of 93.6% and a density of 0.2918 g / cm 3 .

[0082] Example 9

[0083] A method for preparing ZrSiO4 aerogel by sol-gel combined with supercritical drying, comprising the following steps:

[0084] (1) first, 0.1 g of polyvinyl alcohol is dissolved in a mixed solution of anhydrous ethanol and deionized water, and uniformly stirred on a magnetic stirrer; the volume ratio of anhydrous ethanol to deionized water is 1:0.1;

[0085] (2) sodium silicate and zirconyl nitrate are added to the mixed solution containing the crosslinking agent to form a precursor solution; the solution is placed in a 45 ℃ water bath kettle and stirred for 8 h; the concentration ratio of sodium silicate, zirconyl nitrate and polyvinyl alcohol is 1:2:1.2;

[0086] (3) the mixed solution is placed in a 50 ℃ oven, and after 36 h of gelation, it is soaked in ethanol for 60 h;

[0087] (4) the obtained wet gel is placed into a CO2 supercritical drying reaction kettle, the temperature in the reaction kettle is maintained at 4 ℃, liquid CO2 is used for replacement for 72 h; the temperature in the reaction kettle is increased to 40 ℃, and after reaching the supercritical state, 0.6 h is maintained, then pressure is released and the dried gel is taken out;

[0088] (5) the sample after supercritical drying is placed into a muffle furnace, and heated to 1600 ℃ at a rate of 3 ℃ / min under an air atmosphere, and heat preservation is performed for 0.5 h; after cooling to room temperature, ZrSiO4 aerogel with high porosity, low density, good high-temperature resistance and good long-term thermal stability is obtained; the ZrSiO4 aerogel prepared in this embodiment has a porosity of 93.6% and a density of 0.2918 g / cm 3 .

[0089] Example 10

[0090] A method for preparing ZrSiO4 aerogel by sol-gel combined supercritical drying, comprising the following steps:

[0091] (1) First, 0.1 g of sodium carboxymethyl cellulose is dissolved in a mixed solution of anhydrous ethanol and deionized water, and stirred uniformly on a magnetic stirrer; the volume ratio of anhydrous ethanol and deionized water is 1:0.2;

[0092] (2) Methyltrimethoxysilane and zirconium sulfate are added to the mixed solution containing the crosslinking agent to form a precursor solution after stirring uniformly; the solution is placed in a 50℃ water bath for stirring for 12 h; the concentration ratio of sodium silicate, zirconyl nitrate and polyvinyl alcohol is 2:1:1.2;

[0093] (3) The mixed solution is placed in an oven at 60℃, and after gelation for 24 h, it is soaked in ethanol for 72 h;

[0094] (4) The obtained wet gel is placed in a CO2 supercritical drying reaction kettle, the temperature in the reaction kettle is maintained at 4℃, and liquid CO2 is used to replace for 72 h; the temperature in the reaction kettle is increased to 40℃, and when the supercritical state is reached, it is maintained for 0.8 h, then the pressure is released and the dried gel is taken out;

[0095] (5) The sample after supercritical drying is placed in a muffle furnace, heated to 1500℃ at a rate of 5℃ / min in an air atmosphere, and maintained for 12 h; after cooling to room temperature, ZrSiO4 aerogel with high porosity, low density, good high-temperature resistance and long-term thermal stability is obtained; the porosity of the ZrSiO4 aerogel prepared in this example is 96.9%, the density is 0.1414 g / cm 3 .

[0096] Comparative Example 1

[0097] Different from Example 1, in step (5), the temperature is increased to 1550℃ at a rate of 10℃ / min in an air atmosphere in a muffle furnace, and maintained for 15 h, and the rest of the experimental conditions are the same; the product prepared in this comparative example has a porosity of 82.5%, a density of 0.795 g / cm 3 , a pore volume of 1.01 cm 3 / g, a specific surface area of 30.6 m 2 / g, a compressive strength of 1.51 MPa, and a thermal conductivity of 0.25 W·m -1 K -1 .

[0098] Comparative Example 2

[0099] The difference between the example 2 and the present comparative example is that the concentration ratio of dimethyldiethoxysilane, zirconyl nitrate and tartaric acid in step (2) is 1:1:8, and the rest of the experimental conditions are the same; the product prepared in the present comparative example has a porosity of 71.5%, a density of 1.23 g / cm 3 , a pore volume of 0.98 cm 3 / g, a specific surface area of 20.6 m 2 / g, a compressive strength of 1.35 MPa, and a thermal conductivity of 0.43 W·m -1 K -1 .

[0100] Comparative Example 3

[0101] The difference between the example 3 and the present comparative example is that the stirring time in the 95 ℃ water bath is 36 h in step (2), and the rest of the experimental conditions are the same; the product prepared in the present comparative example has a porosity of 81.5%, a density of 0.8436 g / cm 3 , a pore volume of 1.00 cm 3 / g, a specific surface area of 25.9 m 2 / g, a compressive strength of 1.55 MPa, and a thermal conductivity of 0.23 W·m -1 K -1 .

Claims

1. A method for preparing ZrSiO4 aerogel using a sol-gel combination and supercritical drying, characterized in that: Its preparation process includes the following steps: (1) Dissolve the crosslinking agent in a mixed solution of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water is 0.01:1 to 1:0.01, and stir until homogeneous; the crosslinking agent is one or more of malic acid, tartaric acid, polymaleic acid, polyacrylic acid, hexamethylenetetramine, formamide, polyethyleneimine, propylene oxide, polyvinyl alcohol, and sodium carboxymethyl cellulose. (2) Add silicon source and zirconium source to a mixed solution containing crosslinking agent. The concentration ratio of silicon source, zirconium source and crosslinking agent is 1.0~2.0 : 1.0~2.0 : 0.01~4.

0. Stir evenly to form a precursor solution. The temperature range of the raw material stirring is 1~80 ℃ and the stirring time is 0.1~24 h. The silicon source is one or more of tetraethyl orthosilicate, dimethyldiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, γ-aminopropyltriethoxysilane, silica sol and sodium silicate. The zirconium source is one or more of zirconium oxychloride, zirconium oxynitrate, zirconium n-butoxide, zirconium acetate, zirconium sulfate and zirconium isopropoxide. (3) The precursor solution was gelled in an oven, and then the resulting wet gel was immersed in ethanol for displacement. (4) Place the obtained wet gel into a CO2 supercritical drying reactor, maintain the temperature inside the reactor at 4 ℃, and use liquid CO2 for displacement; raise the temperature inside the reactor to make CO2 reach the supercritical state, dry the wet gel, and then depressurize and take out the dried gel. (5) The dried gel was subjected to high-temperature heat treatment to obtain ZrSiO4 aerogel; the heat treatment temperature was 1000~1600 ℃ and the holding time was 0.5~12 h.

2. The method for preparing ZrSiO4 aerogel using a sol-gel combination and supercritical drying as described in claim 1, characterized in that: In step (3), the gel temperature is 30~90 ℃ and the gelation time is 0.5~72 h; the wet gel is soaked in ethanol for 24~72 h.

3. The method for preparing ZrSiO4 aerogel using a sol-gel combination and supercritical drying as described in claim 1, characterized in that: In step (4), the time for CO2 replacement is 0.5~72 h; the time for drying in the supercritical state is 0.1~24 h.

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