Preparation method of silica-stabilized lanthanum zirconate aerogel

Abstract

The application provides a preparation method of silica-stabilized lanthanum zirconate aerogel, and comprises the following steps: using lanthanum nitrate hexahydrate and zirconium nitrate pentahydrate as precursors, and using propylene oxide as a catalyst to obtain an LZ sol in anhydrous ethanol solvent; using tetraethyl orthosilicate as a precursor, and using hydrochloric acid as a catalyst to carry out hydrolysis in an ethanol and water solvent to obtain an SiO2 sol; dropping the obtained SiO2 sol into the LZ sol drop by drop to obtain a mixed solution, and dropping the mixed solution into propylene oxide gel promoter drop by drop to obtain an LZS sol; the LZS sol is placed in an oven to obtain an LZS gel; and the LZS gel is subjected to aging and supercritical drying to obtain a blocky LZS aerogel. The silica-stabilized lanthanum zirconate aerogel has a unique pyrochlore structure and good thermal stability, and has a very large application prospect in the field of heat preservation and insulation.

Description

Technical Field

[0001] This invention belongs to the field of aerogel preparation technology, specifically relating to a method for preparing silica-stabilized lanthanum zirconate aerogel. Background Technology

[0002] Thermal barrier coatings (TBCs) possess excellent thermal insulation and oxidation resistance, making them one of the most advanced high-temperature protective coatings currently available. They are widely used in industries such as aerospace, automotive, and large-scale thermal power generation. The most commonly used TBC material is currently 8 mol% Y₂O₃-ZrO₂ (8YSZ), but its long-term operating temperature is below 1200℃, which no longer meets the needs of future technological development. Lanthanum zirconate, due to its high melting point, stable phase structure, and low thermal conductivity, is considered a promising new high-temperature TBC material. This material possesses a unique pyrochlore structure. Currently, lanthanum zirconate aerogels prepared via the sol-gel method exhibit better high-temperature stability, showing no phase transition between room temperature and melting point. However, the pyrochlore structure, due to the presence of oxygen vacancies, easily accelerates sintering and causes cracks, resulting in poor thermal stability of the aerogel material. Summary of the Invention

[0003] To address the problems in the prior art, this invention provides a method for preparing silica-stabilized lanthanum zirconate aerogel, which yields silica-stabilized lanthanum zirconate aerogel with a unique pyrochlore structure and good thermal stability, showing great promise for application in the field of thermal insulation.

[0004] The technical problem solved by this invention is achieved by the following technical solution:

[0005] The present invention aims to provide a method for preparing silica-stabilized lanthanum zirconate aerogel, characterized by comprising the following steps:

[0006] LZ sol was obtained in anhydrous ethanol solvent using lanthanum nitrate hexahydrate and zirconium nitrate pentahydrate as precursors and propylene oxide as catalyst.

[0007] SiO2 sol was obtained by hydrolysis of tetraethyl orthosilicate as a precursor and hydrochloric acid as a catalyst in ethanol and water solvent.

[0008] The obtained SiO2 sol was added dropwise to LZ sol to obtain a mixed solution. The mixed solution was then added dropwise to propylene oxide gel accelerator to obtain LZS sol.

[0009] The LZS sol was left to stand in an oven to obtain LZS gel;

[0010] The LZS gel was aged and supercritically dried to obtain block LZS aerogel.

[0011] A method for preparing silica-stabilized lanthanum zirconate aerogel, characterized by comprising the following steps:

[0012] 1) Add lanthanum nitrate hexahydrate, zirconium nitrate pentahydrate and ethanol to a beaker in proportion, and stir in a magnetic stirring pan at 80°C until clear and transparent. After standing to room temperature, a mixed solution is obtained.

[0013] 2) Add propylene oxide dropwise into the mixed sol obtained in step 1), and stir until homogeneous to obtain LZ sol;

[0014] 3) Add tetraethyl orthosilicate, ethanol, and water sequentially to a three-necked flask in a molar ratio of 1:14:2, and stir mechanically for 15 min. Then, add hydrochloric acid dropwise through a constant pressure funnel and stir for 120 min. After stirring, seal and let stand at room temperature for 24 h to allow the hydrolysis reaction to proceed fully and slowly, obtaining SiO2 sol.

[0015] 4) Add the SiO2 sol obtained in step 3) dropwise into the LZ sol obtained in step 2) and stir until homogeneous to obtain a mixed solution;

[0016] 5) Add propylene oxide dropwise to the mixed solution obtained in step 4), stir until homogeneous to obtain LZS sol, and place it in an oven to obtain LZS gel.

[0017] 6) The LZS gel obtained above was aged in a sealed environment at room temperature for 72 hours and then subjected to supercritical drying to obtain block LZS aerogel.

[0018] Furthermore, in step 1), the molar ratio of lanthanum nitrate hexahydrate, zirconium nitrate pentahydrate, and ethanol is 1:1:40 to 100.

[0019] Furthermore, in step 1), the reaction temperature is 80℃, and the reaction degree is such that the solution is clear and transparent.

[0020] Furthermore, in step (2), the molar ratio of lanthanum nitrate hexahydrate to propylene oxide is 1:2, and the stirring time is 10 min.

[0021] Furthermore, in step (3), the molar ratio of tetraethyl orthosilicate, ethanol and water is 1:14:2, and the stirring time is 15 min.

[0022] Furthermore, in step (3), the mass fraction of hydrochloric acid is 0.05 wt%, and the molar ratio of tetraethyl orthosilicate to hydrochloric acid is 5:10. -4 .

[0023] Furthermore, in step (3), after adding hydrochloric acid, the mixture is stirred for 120 minutes. After stirring, the mixture is sealed and left to stand at room temperature for 24 hours to allow the hydrolysis reaction to proceed fully and slowly.

[0024] Furthermore, the molar fraction of Si incorporated in step (4) is 4% to 20%.

[0025] Furthermore, in step (5), the molar ratio of lanthanum nitrate hexahydrate to propylene oxide is 1:1.

[0026] Furthermore, in step (5), the oven temperature is set to 60°C.

[0027] Furthermore, the aging time of the gel in step (6) is 72 hours.

[0028] Furthermore, the supercritical ethanol drying method is as follows: using ethanol as the supercritical drying medium, pre-purging with nitrogen to ensure the pressure inside the reactor is not less than 2 MPa, raising the temperature inside the reactor to 270°C at a heating rate of 1°C / min, and holding at this temperature for 2 hours until the pressure inside the reactor is 8–10 MPa. After turning on the water cooling device and slowly releasing the pressure inside the reactor to atmospheric pressure, N2 is introduced to purge the reactor, and after cooling to room temperature, LZS aerogel is obtained.

[0029] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0030] This invention uses rare earth nitrates and tetraethyl orthosilicate as raw materials, ethanol as solvent, and acid and alkali as catalysts to prepare silicon-modified lanthanum zirconate wet gel using the sol-gel method. After supercritical drying with ethanol, blocky silica-stabilized lanthanum zirconate aerogel is obtained. The prepared aerogel has low density, high specific surface area, and good thermal insulation performance.

[0031] The preparation method of this invention has low equipment requirements, short processing time, and a simple preparation process, making it suitable for large-scale production. This process can reduce the density of lanthanum zirconate aerogel and improve its formability and thermal stability. By controlling the ethanol content and the molar fraction of SiO2 incorporated, the density and structure of the aerogel can be controlled, thereby further controlling its thermal conductivity. Incorporating SiO2 into lanthanum zirconate aerogel can yield a complete bulk structure, thereby improving the thermal stability of the aerogel.

[0032] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above contents, objectives, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0033] Figure 1 This is a macroscopic image of the LZS aerogel obtained in Example 1 of the preparation method of silica-stabilized lanthanum zirconate aerogel of the present invention.

[0034] Figure 2The N2 adsorption-desorption curve and pore size distribution diagram of the LZS aerogel obtained in Example 1 of the preparation method of silica-stabilized lanthanum zirconate aerogel of the present invention are shown.

[0035] Figure 3 This is a SEM microstructure image of the LZS aerogel obtained in Example 1 of the preparation method of silica-stabilized lanthanum zirconate aerogel of the present invention.

[0036] Figure 4 The images show the XRD patterns of LZS aerogels obtained in Examples 1 and 3 of the present invention after heat treatment at 1200℃ in the preparation method of silica-stabilized lanthanum zirconate aerogel. Detailed Implementation

[0037] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0038] In addition, unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or prepared by existing methods.

[0039] Example 1:

[0040] A method for preparing silica-stabilized lanthanum zirconate aerogel, comprising the following steps:

[0041] 1) Add 2.598g of lanthanum nitrate hexahydrate, 2.5759g of zirconium nitrate pentahydrate and 11.0568g of anhydrous ethanol to a beaker in sequence, and stir in a magnetic stirring pan at 80℃ until clear and transparent. After standing to room temperature, a mixed solution is obtained.

[0042] 2) Add 0.6969g of propylene oxide dropwise to the mixed sol obtained in step 1), and stir until homogeneous to obtain LZ sol.

[0043] 3) Add 5g TEOS, 15.456g anhydrous ethanol, and 0.864g H2O to a three-necked flask and stir mechanically for 15min. Then, add 0.864g of a 0.05wt% hydrochloric acid-ethanol dilution solution dropwise through a constant pressure funnel at a rate of 6s / drop and stir for 120min. After stirring, seal and let stand at room temperature for 24h to allow the hydrolysis reaction to proceed fully and slowly, obtaining SiO2 sol.

[0044] 4) Slowly drop 0.7579g of the SiO2 sol obtained in step 3) into the LZ sol obtained in step 2), and stir magnetically for 30 minutes to obtain a mixed solution with a SiO2 doping amount of 12% molar fraction.

[0045] 5) 0.3485g of propylene oxide is added dropwise to the material obtained in step 4), and after stirring evenly, SiO2 sol is obtained. It is then placed in an oven at 60℃ and allowed to stand to obtain a wet gel.

[0046] 6) After the LZS gel was sealed and allowed to age for 72 hours, it was subjected to supercritical drying using ethanol as the supercritical drying medium and pre-charged with N2 until the pressure inside the reactor reached 2 MPa. The temperature inside the reactor was raised to 270°C at a heating rate of 1°C / min and held at this temperature for 2 hours until the pressure inside the reactor reached 10 MPa. The water cooling device was turned on, and the pressure inside the reactor was slowly released to atmospheric pressure. Then, N2 was introduced to purge the reactor, and after cooling to room temperature, LZS aerogel was obtained.

[0047] See appendix Figure 1 The image shows a macroscopic view of the blocky LZS aerogel obtained in this example. The density of the obtained aerogel is 0.1573 g / cm³. 3 Its thermal conductivity is 0.0379 W / mK, and its specific surface area is 452.7 m². 2 / g. (Attached) Figure 2 The attached diagram shows the N2 adsorption-desorption curves and pore size distribution of this embodiment. Figure 3 Here is a diagram of the microstructure of the aerogel, attached. Figure 4 The XRD pattern of LZS aerogel after heat treatment at 1200℃ shows that the isotherms of LZS aerogel exhibit typical type III isotherms and have H3-type hysteresis loops, indicating the characteristic distribution of slit-like pores with diameters between 20 and 40 nm. After heat treatment at 1200℃, La2Zr2O7 becomes the main component, and the addition of SiO2 enhances the stability of lanthanum zirconate aerogel.

[0048] Example 2:

[0049] A method for preparing silica-stabilized lanthanum zirconate aerogel, comprising the following steps:

[0050] 1) Add 2.598g of lanthanum nitrate hexahydrate, 2.5759g of zirconium nitrate pentahydrate and 22.1136g of anhydrous ethanol to a beaker in sequence, and stir in a magnetic stirring pan at 80℃ until clear and transparent. After standing to room temperature, a mixed solution is obtained.

[0051] 2) Add 0.6969g of propylene oxide dropwise to the mixed sol obtained in step 1), and stir until homogeneous to obtain LZ sol.

[0052] 3) Add 5g TEOS, 15.456g anhydrous ethanol, and 0.864g H2O to a three-necked flask and stir mechanically for 15min. Then, add 0.864g of a 0.05wt% hydrochloric acid-ethanol dilution solution dropwise through a constant pressure funnel at a rate of 6s / drop and stir for 120min. After stirring, seal and let stand at room temperature for 24h to allow the hydrolysis reaction to proceed fully and slowly, obtaining SiO2 sol.

[0053] 4) Slowly drop 0.7579g of the SiO2 sol obtained in step 3) into the LZ sol obtained in step 2), and stir magnetically for 30 minutes to obtain a mixed solution with a Si doping amount of 12% molar fraction.

[0054] 5) 0.3485g of propylene oxide is added dropwise to the material obtained in step 4), and after stirring evenly, SiO2 sol is obtained. It is then placed in an oven at 60℃ and allowed to stand to obtain a wet gel.

[0055] 6) After the LZS gel was sealed and allowed to age for 72 hours, it was subjected to supercritical drying using ethanol as the supercritical drying medium and pre-charged with N2 until the pressure inside the reactor reached 2 MPa. The temperature inside the reactor was raised to 270°C at a heating rate of 1°C / min and held at this temperature for 2 hours until the pressure inside the reactor reached 10 MPa. The water cooling device was turned on, and the pressure inside the reactor was slowly released to atmospheric pressure. Then, N2 was introduced to purge the reactor, and after cooling to room temperature, LZS aerogel was obtained.

[0056] The density of the blocky LZS aerogel obtained in Example 2 is 0.0788 g / cm³. 3 It has a thermal conductivity of 0.0368 W / mK and a specific surface area of ​​436.9 m². 2 / g. It is evident that the amount of solvent added during the LZ sol preparation process has a significant impact on the density of LZS aerogel. The amount of solvent added during the LZ sol preparation process is: n 六水硝酸镧 :n 五水硝酸锆 :n 乙醇 =1:1:40~100.

[0057] Example 3:

[0058] A method for preparing silica-stabilized lanthanum zirconate aerogel, comprising the following steps:

[0059] 1) Add 2.598g of lanthanum nitrate hexahydrate, 2.5759g of zirconium nitrate pentahydrate and 11.0568g of anhydrous ethanol to a beaker in sequence, and stir in a magnetic stirring pan at 80℃ until clear and transparent. After standing to room temperature, a mixed solution is obtained.

[0060] 2) Add 0.6969g of propylene oxide dropwise to the mixed sol obtained in step 1), and stir until homogeneous to obtain LZ sol.

[0061] 3) Add 5g TEOS, 15.456g anhydrous ethanol, and 0.864g H2O to a three-necked flask and stir mechanically for 15min. Then, add 0.864g of a 0.05wt% hydrochloric acid-ethanol dilution solution dropwise through a constant pressure funnel at a rate of 6s / drop and stir for 120min. After stirring, seal and let stand at room temperature for 24h to allow the hydrolysis reaction to proceed fully and slowly, obtaining SiO2 sol.

[0062] 4) Slowly drop 0.4806g of the SiO2 sol obtained in step 3) into the LZ sol obtained in step 2), and stir magnetically for 30 minutes to obtain a mixed solution with a Si doping amount of 8% molar fraction.

[0063] 5) 0.3485g of propylene oxide is added dropwise to the material obtained in step 4), and after stirring evenly, SiO2 sol is obtained. It is then placed in an oven at 60℃ and allowed to stand to obtain a wet gel.

[0064] 6) After the LZS gel was sealed and allowed to age for 72 hours, it was subjected to supercritical drying using ethanol as the supercritical drying medium and pre-charged with N2 until the pressure inside the reactor reached 2 MPa. The temperature inside the reactor was raised to 270°C at a heating rate of 1°C / min and held at this temperature for 2 hours until the pressure inside the reactor reached 10 MPa. The water cooling device was turned on, and the pressure inside the reactor was slowly released to atmospheric pressure. Then, N2 was introduced to purge the reactor, and after cooling to room temperature, LZS aerogel was obtained.

[0065] The density of the blocky LZS aerogel obtained in Example 3 was 0.199 g / cm³. 3 Its thermal conductivity is 0.0321 W / mK, and its specific surface area is 462.8 m². 2 / g. (Attached) Figure 4 The XRD curves after heat treatment at 1200℃ show that, in this embodiment, the thermal conductivity increased after the SiO2 content was reduced, and the XRD of the aerogel remained almost unchanged. The peaks of La2Zr2O7 and zirconia were enhanced to some extent, indicating that adding an appropriate amount of SiO2 can effectively improve the thermal stability of the aerogel.

[0066] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0067] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing silica-stabilized lanthanum zirconate aerogel, characterized in that, Includes the following steps: 1) Add lanthanum nitrate hexahydrate, zirconium nitrate pentahydrate and ethanol to a beaker in proportion, and stir in a magnetic stirring pan at 80°C until clear and transparent. After standing to room temperature, a mixed solution is obtained. 2) Add propylene oxide dropwise into the mixed sol obtained in step 1), and stir until homogeneous to obtain LZ sol; 3) Add tetraethyl orthosilicate, ethanol and water to a three-necked flask in the specified proportions, stir mechanically for 15 min, add hydrochloric acid dropwise through a constant pressure funnel, stir for 120 min, and after stirring, seal and let stand at room temperature for 24 h to allow the hydrolysis reaction to proceed fully and slowly, and obtain SiO2 sol. 4) The SiO2 sol obtained in step 3) is added dropwise to the LZ sol obtained in step 2) and stirred evenly to obtain a mixed solution with a Si molar fraction of 4% to 20%. 5) Add propylene oxide dropwise to the mixed solution obtained in step 4), stir until homogeneous to obtain LZS sol, and place it in an oven to obtain LZS gel. 6) The LZS gel obtained above was aged in a sealed environment at room temperature for 72 hours and then subjected to supercritical drying to obtain block LZS aerogel.

2. The method for preparing a silica-stabilized lanthanum zirconate aerogel as described in claim 1, characterized in that: In step 1), the molar ratio of lanthanum nitrate hexahydrate, zirconium nitrate pentahydrate, and ethanol is 1:1:40 to 100.

3. The method for preparing a silica-stabilized lanthanum zirconate aerogel as described in claim 1, characterized in that: In step 1), the reaction temperature is 80℃, and the reaction is complete when the solution is clear and transparent.

4. The method for preparing a silica-stabilized lanthanum zirconate aerogel as described in claim 1, characterized in that: In step 2), the molar ratio of lanthanum nitrate hexahydrate to propylene oxide is 1:2, and the stirring time is 10 min.

5. The method for preparing a silica-stabilized lanthanum zirconate aerogel as described in claim 1, characterized in that: In step 3), the molar ratio of tetraethyl orthosilicate, ethanol and water is 1:14:2, and the stirring time is 15 min.

6. The method for preparing a silica-stabilized lanthanum zirconate aerogel as described in claim 1, characterized in that: In step 3), the mass fraction of hydrochloric acid is 0.05 wt%, and the molar ratio of tetraethyl orthosilicate to hydrochloric acid is 5:

10. -4 .

7. The method for preparing a silica-stabilized lanthanum zirconate aerogel as described in claim 1, characterized in that: In step 5), the molar ratio of lanthanum nitrate hexahydrate to propylene oxide is 1:1.

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