A low cost method for the preparation of a silica calcium based aerogel material and the product prepared thereby

Abstract

This invention provides a low-cost preparation method for a calcium silicate-based aerogel material and the product thereof, relating to the field of calcium silicate-based aerogels. The low-cost preparation method for the calcium silicate-based aerogel material includes the following steps: sol-gel, impurity washing, high-temperature aging, and microwave drying. This invention's low-cost preparation method for calcium silicate-based aerogel materials can utilize inexpensive calcium and silicon sources, and obtain calcium silicate-based aerogel products through a simple and efficient preparation process. The process is easy to control, has good process stability, and good batch consistency, making it suitable for large-scale industrial production. Furthermore, no organic solvents are required during the preparation process, effectively avoiding the adverse effects caused by organic solvents. Under the aforementioned conditions, it can further improve the mechanical properties, thermal insulation properties, and high-temperature stability of the calcium silicate-based aerogel.

Description

Technical Field

[0001] This invention relates to the field of calcium silicate aerogels, and in particular to a low-cost preparation method for calcium silicate aerogel materials and the products prepared therefrom. Background Technology

[0002] Aerogels have a special nanoporous structure and are currently the solid materials with the lowest thermal conductivity at room temperature. They are widely used in oil pipelines, heating networks, nuclear power, storage tank equipment, tank armor, rail transportation, ships, aerospace and other fields. Existing aerogel materials are mainly silica aerogels. In downstream applications, they have the following technical problems: (1) Silica aerogels have low temperature resistance, with a maximum operating temperature of only 800℃, making them difficult to use alone in high-temperature fields; (2) Silica aerogels have poor mechanical properties and are usually difficult to use alone. They need to be used in combination with other materials, but the combination will greatly reduce the thermal insulation performance of silica aerogels.

[0003] Calcium silicate possesses excellent high-temperature resistance and mechanical properties. Preparing calcium silicate into an aerogel state yields structurally stable and high-performance calcium silicate aerogel products, which have profound implications for applications in high-temperature fields and even building materials. However, existing calcium silicate aerogel preparation processes require large amounts of organic solvents, and subsequent drying and solvent recovery steps are complex, energy-intensive, and involve significant equipment investment, resulting in high overall production costs and hindering effective promotion in the civilian sector.

[0004] Chinese patent CN119430206A discloses a method for preparing a low-cost, rapid freeze-drying calcium silicate aerogel. The method involves mixing a calcium source and a silicon source to form a calcium silicate sol, followed by gelation with a coagulant such as propylene oxide or epichlorohydrin, and then hydrophobic modification with an organic solvent solution containing a hydrophobic modifier. Finally, the aerogel is obtained through freeze-drying and high-temperature calcination. However, this method still has the following technical defects: (1) The propylene oxide or epichlorohydrin used as a coagulant has strong chemical activity, making it difficult to control during preparation, resulting in poor process stability, poor batch consistency, and hindering its application to large-scale industrial production; (2) The use of an organic solvent solution containing a hydrophobic modifier still involves the use, removal, and recycling of organic solvents, making the overall preparation process cumbersome and costly; furthermore, after hydrophobic modification, a large amount of organic solvent washing or specific physical treatment is required to remove the organic solvents from the gel, which not only further increases the amount of organic solvent used or production energy consumption but may also fail to effectively remove residual organic solvents from the gel, thus affecting the aerogel. Performance; taking the aforementioned patent's technical solution as an example, it uses anhydrous ethanol as the solvent for the hydrophobic modifier. During the freeze-drying process after hydrophobic modification, the freeze-drying pretreatment temperature is only -50°C to -60°C, which is much higher than the freezing point of ethanol (-114°C). Conventional equipment and methods cannot reduce the temperature to such a low level, and the cooling energy consumption is huge, making it impossible to promote large-scale industrial production. It also directly leads to the extremely low efficiency and effect of the existing freeze-drying process in removing organic solvents from the gel. The residual ethanol will damage the aerogel network structure during freeze-drying and high-temperature calcination, and the carbon residues remaining in the aerogel matrix will ultimately affect the mechanical properties, thermal insulation properties, and high-temperature stability of the prepared aerogel. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a low-cost preparation method for calcium-silicon-based aerogel materials. This method utilizes inexpensive calcium and silicon sources and employs a simple and efficient preparation process to produce calcium-silicon-based aerogel products. The process is easy to control, exhibits good process stability, and ensures good batch-to-batch consistency, making it suitable for large-scale industrial production. Furthermore, no organic solvents are required during the preparation process, effectively avoiding the adverse effects caused by organic solvents. Moreover, this method further improves the mechanical properties, thermal insulation properties, and high-temperature stability of the calcium-silicon-based aerogel. This invention also provides calcium-silicon-based aerogel products prepared using this method.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A low-cost preparation method for a silicon-calcium based aerogel material, characterized by comprising the following steps: sol-gel, impurity washing, high-temperature aging, and microwave drying;

[0008] The sol-gel method involves adjusting the pH of the silicon source solution to 4-6 using an acidic catalyst, then mixing it evenly with a calcium source solution to obtain a silicon-calcium sol; the silicon-calcium sol is then allowed to stand and gel to obtain a silicon-calcium gel.

[0009] The method for washing away the impurities is to wash the calcium silicate gel with deionized water;

[0010] The high-temperature aging method involves placing the washed calcium silicate gel in deionized water, controlling the aging temperature at 180-300℃ and the aging pressure at 8.5-10MPa in a closed environment, and then performing high-temperature aging treatment to obtain the preform.

[0011] The preform was microwave dried to obtain a silicon-calcium based aerogel.

[0012] Preferably, in the sol-gel process, the temperature of the gel during standing is 50-70°C, and the relative humidity is not less than 90%.

[0013] The gel should be allowed to stand for 0.5-1 hour.

[0014] Preferably, in the sol-gel, the silicon source used in the silicon source solution is liquid water glass; the liquid water glass has a silicon dioxide content >25% and a modulus >3.0;

[0015] The calcium source used in the calcium source solution is one of the following: calcium chloride, calcium nitrate, calcium formate, calcium acetate, or calcium lactate;

[0016] The hydrogen ion concentration in the acidic catalyst is 1-3 mol / L, and the acidic catalyst is one of the following: hydrochloric acid, nitric acid, formic acid, acetic acid, or lactic acid.

[0017] Preferably, in the sol-gel, the volume ratio of silicon source to deionized water in the silicon source solution is 1:1-3;

[0018] The CaO content in the calcium source solution is 5-30 wt%;

[0019] The mixing of silicon source solution and calcium source solution must meet the following requirements: the molar ratio of SiO2 in silicon source solution to CaO in calcium source solution is 1-3:1.

[0020] Preferably, in the impurity washing process, the volume ratio of silica-calcium gel to deionized water is 1:3-5;

[0021] Deionized water should be changed every 8-12 hours, for a total of 3-4 times.

[0022] Preferably, in the high-temperature aging process, the volume ratio of the washed calcium silicate gel to deionized water is 1:1-2.

[0023] The high-temperature aging treatment with heat preservation and pressure preservation time is 12-24 hours.

[0024] Furthermore, the microwave treatment method involves controlling the microwave frequency to 2400-2500MHz and sequentially performing a first microwave drying treatment, a second microwave drying treatment, and a third microwave drying treatment on the preform to obtain a calcium-silicon-based aerogel.

[0025] Preferably, the microwave power density is controlled to be 3.5-4 W / g in the first microwave drying process;

[0026] In the second microwave drying process, the microwave power density is controlled to be 2.5-3 W / g;

[0027] In the third microwave drying process, the microwave power density is controlled to be 1.8-2.2 W / g.

[0028] Preferably, the microwave drying temperature of the first microwave drying treatment is 100-105℃ and the microwave drying time is 10-15 min; the microwave drying temperature of the second microwave drying treatment is 120-125℃ and the microwave drying time is 40-50 min; and the microwave drying temperature of the third microwave drying treatment is 135-140℃ and the microwave drying time is 10-20 min.

[0029] A silicon-calcium based aerogel product prepared using the aforementioned method.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) The low-cost preparation method of the silicon-calcium based aerogel material of the present invention uses inexpensive and readily available industrial-grade liquid water glass as the silicon source in the sol-gel step. It is combined with a calcium source and the pH of the sol is controlled within a predetermined range by an acidic catalyst. This promotes the hydrolysis, condensation and polymerization of silicon-calcium ions in a specific ratio within a predetermined pH range, and finally transforms them into a gel. In the impurity washing step, the silicon-calcium gel is washed with deionized water to thoroughly remove residual water-soluble by-product impurities and acidic catalyst components in the pores of the silicon-calcium gel. This lays the foundation for the effective implementation of subsequent high-temperature aging and microwave drying processes and is conducive to improving the performance of the silicon-calcium aerogel material. In the high-temperature aging step, the silicon-calcium gel is in a closed water bath environment under the subcritical state of high temperature and high pressure water. This further promotes the condensation of residual groups in the gel skeleton, thereby forming more covalent bonds and optimizing the aerogel structure. This specifically improves the mechanical properties and stability of the aerogel skeleton. Qualitatively, in the microwave drying step, during the sequential first, second, and third microwave drying processes, the free and bound water of the preform are effectively removed under the premise of controllable drying and dehydration rate by controlling the predetermined microwave power density and microwave drying temperature at each stage. This maximizes the preservation of the integrity of the aerogel network structure and pore structure, ensuring the high specific surface area, high thermal insulation, and high structural strength of the prepared calcium-silicon silicate aerogel. The aforementioned technologies work together synergistically, enabling the production of calcium-silicon silicate aerogel products using inexpensive calcium and silicon sources through a simple and efficient preparation process. The process is easy to control, has good process stability, and good batch consistency, making it suitable for large-scale industrial production. Furthermore, no organic solvents are required during the preparation process, effectively avoiding the adverse effects caused by organic solvents. Under the aforementioned conditions, the mechanical properties, thermal insulation properties, and high-temperature stability of the calcium-silicon silicate aerogel can be further improved.

[0032] (2) The product prepared using the low-cost preparation method of the silicon-calcium based aerogel material of the present invention has a density of 0.04-0.06 g / cm³. 3 The average pore size is 15-25 nm, and the specific surface area is 450-600 m². 2 / g, compressive strength is 1.11-1.23MPa, thermal conductivity at room temperature is 0.021-0.024W / m·k, and the compressive strength retention rate after heat treatment at 800℃ for 1h is 94.9-96.0%.

[0033] (3) The low-cost preparation method of the silicon-calcium-based aerogel material of the present invention does not require the use of any organic solvents in the preparation process, effectively avoiding the problems of use, removal, recycling and solvent residue caused by the use of organic solvents, effectively reducing production costs and energy consumption, and is highly environmentally friendly.

[0034] (4) The low-cost preparation method of the silicon-calcium based aerogel material of the present invention has inexpensive and readily available raw materials, simple and efficient preparation process, easy control of preparation process, good process stability, good batch consistency of product, and is suitable for large-scale industrial production. Detailed Implementation

[0035] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] This invention provides a low-cost preparation method for a silicon-calcium based aerogel material, comprising the following steps: sol-gel, impurity washing, high-temperature aging, and microwave drying.

[0038] The sol-gel method involves mixing silicon source and calcium source with deionized water at a certain volume ratio to obtain silicon source solution and calcium source solution, respectively; adjusting the pH of silicon source solution to 4-6 using an acidic catalyst, and then mixing it with calcium source solution at a certain ratio to obtain silicon-calcium sol; placing the silicon-calcium sol in a constant temperature and humidity environment at 50-70℃ and relative humidity not less than 90%, and allowing it to stand for 0.5-1 hours to obtain silicon-calcium gel.

[0039] In the sol-gel, the silicon source is industrial-grade liquid water glass with a silica content >25% and a modulus >3.0. The calcium source is one of the following: calcium chloride, calcium nitrate, calcium formate, calcium acetate, or calcium lactate; preferably calcium acetate or calcium lactate.

[0040] In the sol-gel, the volume ratio of silicon source to deionized water in the silicon source solution is 1:1-3; the CaO content in the calcium source solution is 5-30 wt%. The mixing of the silicon source solution and the calcium source solution meets the following requirements: the molar ratio of SiO2 in the silicon source solution to CaO in the calcium source solution is 1-3:1.

[0041] In the sol-gel, the acidic catalyst is one of the following: hydrochloric acid, nitric acid, formic acid, acetic acid, or lactic acid; preferably acetic acid or lactic acid. The hydrogen ion concentration in the acidic catalyst is 1-3 mol / L.

[0042] In the sol-gel step of this invention, inexpensive and readily available industrial-grade liquid water glass is used as the silicon source, combined with a calcium source. An acidic catalyst is used to control the pH of the sol within a predetermined range, which promotes the hydrolysis, condensation and polymerization of silicon and calcium ions in a specific ratio within a predetermined pH range, ultimately transforming the sol into a gel.

[0043] The method for washing impurities is as follows: wash the calcium silicate gel with 3-5 times the volume of deionized water, and change the deionized water every 8-12 hours for a total of 3-4 times; during the impurity washing process, the recovered washing water is purified and reused for impurity washing or high-temperature aging steps.

[0044] In the impurity washing step of this embodiment of the invention, deionized water is used to wash the silica-calcium gel to thoroughly remove residual water-soluble by-product impurities and acidic catalyst components in the pores of the silica-calcium gel. This lays the foundation for the effective implementation of subsequent high-temperature aging and microwave drying processes and helps to improve the performance of silica-calcium aerogel materials.

[0045] The high-temperature aging method involves placing the washed calcium silicate gel in 1-2 times its volume of deionized water in a sealed water bath environment, controlling the aging temperature at 180-300℃ and the aging pressure at 8.5-10MPa, and maintaining the temperature and pressure for aging for 12-24 hours to obtain the preform.

[0046] In the high-temperature aging step of this invention, the calcium silicate gel is placed in a closed water bath environment under the subcritical state of water at high temperature and pressure, which further promotes the condensation of residual groups in the gel skeleton, thereby forming more covalent bonds and optimizing the aerogel structure, and specifically improving the mechanical properties and stability of the aerogel skeleton.

[0047] The microwave drying method involves controlling the microwave frequency at 2400-2500MHz and sequentially performing a first microwave drying treatment, a second microwave drying treatment, and a third microwave drying treatment on the preform to obtain a calcium-silicon-based aerogel. Specifically, in the first microwave drying treatment, the microwave power density is controlled at 3.5-4W / g preform, the microwave drying temperature is 100-105℃, and the microwave drying time is 10-15min; in the second microwave drying treatment, the microwave power density is controlled at 2.5-3W / g preform, the microwave drying temperature is 120-125℃, and the microwave drying time is 40-50min; in the third microwave drying treatment, the microwave power density is controlled at 1.8-2.2W / g preform, the microwave drying temperature is 135-140℃, and the microwave drying time is 10-20min.

[0048] In the microwave drying step of this invention embodiment, during the first microwave drying treatment, the second microwave drying treatment, and the third microwave drying treatment performed sequentially, the free water and bound water of the preform are effectively removed under the premise that the drying and dehydration rate is controllable by using the predetermined microwave power density and microwave drying temperature at each stage. This maximizes the preservation of the integrity of the aerogel network structure and pore structure, ensuring the high specific surface area, high thermal insulation and high structural strength of the prepared silicon-calcium based aerogel.

[0049] The present invention also provides a silicon-calcium based aerogel product prepared by the aforementioned method.

[0050] The present invention will be further described below with reference to some specific embodiments.

[0051] Example 1

[0052] This embodiment provides a low-cost preparation method for a silicon-calcium based aerogel material, specifically:

[0053] (1) Sol-gel

[0054] The silicon source and calcium source were mixed evenly with deionized water to obtain silicon source solution and calcium source solution respectively. The pH of the silicon source solution was adjusted to 4.5 using an acidic catalyst (lactic acid with a hydrogen ion concentration of 1.5 mol / L), and then mixed evenly with the calcium source solution to obtain silicon-calcium sol. The silicon-calcium sol was placed in a constant temperature and humidity environment at 50℃ and 95% relative humidity and allowed to stand for 1 hour to obtain silicon-calcium gel.

[0055] The silicon source is industrial-grade liquid water glass with a silicon dioxide content of 25.6% and a modulus of 3.2; the calcium source is calcium lactate.

[0056] The volume ratio of silicon source to deionized water in the silicon source solution is 1:1.5; the CaO content in the calcium source solution is 15wt%. The mixing of the silicon source solution and the calcium source solution meets the following requirement: the molar ratio of SiO2 in the silicon source solution to CaO in the calcium source solution is 2:1.

[0057] (2) Washing off impurities

[0058] The silica-calcium gel was washed with three times its volume of deionized water, and the deionized water was replaced every 8 hours for a total of 4 times. During the impurity washing process, the recovered washing water was purified and reused for impurity washing or high-temperature aging steps.

[0059] (3) High temperature aging

[0060] The washed calcium silicate gel was placed in 1.2 times its volume of deionized water and aged in a closed water bath at a controlled temperature of 180°C and an aging pressure of 8.5 MPa for 12 hours to obtain the preform.

[0061] (4) Microwave drying

[0062] A calcium-silicon-based aerogel was prepared by sequentially subjecting the preform to a first microwave drying treatment, a second microwave drying treatment, and a third microwave drying treatment, with the microwave frequency controlled at 2450 MHz. Specifically, in the first microwave drying treatment, the microwave power density was controlled at 3.5 W / g preform, the microwave drying temperature at 100 ℃, and the microwave drying time at 10 min; in the second microwave drying treatment, the microwave power density was controlled at 2.5 W / g preform, the microwave drying temperature at 120 ℃, and the microwave drying time at 40 min; and in the third microwave drying treatment, the microwave power density was controlled at 1.8 W / g preform, the microwave drying temperature at 135 ℃, and the microwave drying time at 10 min.

[0063] This embodiment also provides a calcium silicate-based aerogel product prepared by the aforementioned method. The density of this calcium silicate-based aerogel product is measured to be 0.042 g / cm³. 3 The average pore size is 16 nm, and the specific surface area is 557 m². 2 / g, compressive strength is 1.11MPa, thermal conductivity at room temperature is 0.021W / m·k, and compressive strength retention rate after heat treatment at 800℃ for 1h is 94.9%.

[0064] Example 2

[0065] This embodiment provides a low-cost preparation method for a silicon-calcium based aerogel material, specifically:

[0066] (1) Sol-gel

[0067] The silicon source and calcium source were mixed evenly with deionized water to obtain silicon source solution and calcium source solution respectively. The pH of the silicon source solution was adjusted to 4.5 using an acidic catalyst (acetic acid with a hydrogen ion concentration of 1.5 mol / L), and then mixed evenly with the calcium source solution to obtain silicon-calcium sol. The silicon-calcium sol was placed in a constant temperature and humidity environment of 60℃ and 95% relative humidity and allowed to stand for 1 hour to obtain silicon-calcium gel.

[0068] The silicon source is industrial-grade liquid water glass with a silicon dioxide content of 25.6% and a modulus of 3.2; the calcium source is calcium acetate.

[0069] The volume ratio of silicon source to deionized water in the silicon source solution is 1:2; the CaO content in the calcium source solution is 21 wt%. The mixing of the silicon source solution and the calcium source solution meets the following requirement: the molar ratio of SiO2 in the silicon source solution to CaO in the calcium source solution is 2:1.

[0070] (2) Washing off impurities

[0071] The silica-calcium gel was washed with four times its volume of deionized water, and the deionized water was replaced every 10 hours for a total of four times. During the impurity washing process, the recovered washing water was purified and reused for impurity washing or high-temperature aging steps.

[0072] (3) High temperature aging

[0073] The washed calcium silicate gel was placed in 1.5 times its volume of deionized water and aged in a closed water bath at a controlled temperature of 230°C and an aging pressure of 9.5 MPa for 16 hours to obtain the preform.

[0074] (4) Microwave drying

[0075] A calcium-silicon-based aerogel was prepared by sequentially subjecting the preform to a first microwave drying treatment, a second microwave drying treatment, and a third microwave drying treatment at a microwave frequency of 2450 MHz. Specifically, in the first microwave drying treatment, the microwave power density was controlled at 3.8 W / g preform, the microwave drying temperature at 102℃, and the microwave drying time at 13 min; in the second microwave drying treatment, the microwave power density was controlled at 2.8 W / g preform, the microwave drying temperature at 122℃, and the microwave drying time at 45 min; and in the third microwave drying treatment, the microwave power density was controlled at 2 W / g preform, the microwave drying temperature at 138℃, and the microwave drying time at 15 min.

[0076] This embodiment also provides a calcium silicate-based aerogel product prepared by the aforementioned method. The density of this calcium silicate-based aerogel product is measured to be 0.046 g / cm³. 3 The average pore size is 20 nm, and the specific surface area is 519 m². 2 / g, compressive strength is 1.20MPa, thermal conductivity at room temperature is 0.022W / m·k, and the compressive strength retention rate after heat treatment at 800℃ for 1h is 95.2%.

[0077] Example 3

[0078] This embodiment provides a low-cost preparation method for a silicon-calcium based aerogel material, specifically:

[0079] (1) Sol-gel

[0080] The silicon source and calcium source were mixed evenly with deionized water to obtain silicon source solution and calcium source solution respectively. The pH of the silicon source solution was adjusted to 5 using an acidic catalyst (acetic acid with a hydrogen ion concentration of 1.5 mol / L), and then mixed evenly with the calcium source solution to obtain silicon-calcium sol. The silicon-calcium sol was placed in a constant temperature and humidity environment of 70℃ and 95% and allowed to stand for 0.5 h to obtain silicon-calcium gel.

[0081] The silicon source is industrial-grade liquid water glass with a silicon dioxide content of 25.6% and a modulus of 3.2; the calcium source is calcium acetate.

[0082] The volume ratio of silicon source to deionized water in the silicon source solution is 1:2.5; the CaO content in the calcium source solution is 25wt%. The mixing of the silicon source solution and the calcium source solution meets the following requirement: the molar ratio of SiO2 in the silicon source solution to CaO in the calcium source solution is 2.8:1.

[0083] (2) Washing off impurities

[0084] The silica-calcium gel was washed with 5 times its volume of deionized water, and the deionized water was replaced every 12 hours for a total of 4 times. During the impurity washing process, the recovered washing water was purified and reused for impurity washing or high-temperature aging steps.

[0085] (3) High temperature aging

[0086] The washed calcium silicate gel was placed in twice the volume of deionized water and aged in a closed water bath at a controlled temperature of 300℃ and an aging pressure of 10MPa for 14 hours to obtain the preform.

[0087] (4) Microwave drying

[0088] A calcium-silicon-based aerogel was prepared by sequentially subjecting the preform to a first microwave drying treatment, a second microwave drying treatment, and a third microwave drying treatment, with the microwave frequency controlled at 2450 MHz. Specifically, in the first microwave drying treatment, the microwave power density was controlled at 4 W / g preform, the microwave drying temperature at 105 ℃, and the microwave drying time at 15 min; in the second microwave drying treatment, the microwave power density was controlled at 3 W / g preform, the microwave drying temperature at 125 ℃, and the microwave drying time at 50 min; and in the third microwave drying treatment, the microwave power density was controlled at 2.2 W / g preform, the microwave drying temperature at 140 ℃, and the microwave drying time at 20 min.

[0089] This embodiment also provides a calcium silicate-based aerogel product prepared by the aforementioned method. The density of this calcium silicate-based aerogel product is measured to be 0.054 g / cm³. 3 The average pore size is 24 nm, and the specific surface area is 472 m². 2 / g, compressive strength is 1.23MPa, thermal conductivity at room temperature is 0.024W / m·k, and the compressive strength retention rate after heat treatment at 800℃ for 1h is 96.0%.

[0090] Comparative Example 1

[0091] Comparative Example 1 adopts the technical solution of Example 1, the difference being: (1) a conventional aging process is used instead of high temperature aging, and the washed calcium silicate gel is placed in a normal pressure environment at 70°C and allowed to stand for 48 hours; (2) in microwave drying, the microwave frequency is controlled at 2450MHz, the microwave power density is 3W / g preform, the microwave drying temperature is 125°C, and the microwave drying time is 70min.

[0092] The density of the silica-calcium based aerogel product in Comparative Example 1 was tested to be 0.076 g / cm³. 3 The average pore size is 12 nm, and the specific surface area is 418 m². 2 / g, compressive strength is 0.38MPa, thermal conductivity at room temperature is 0.030W / m·k, and the compressive strength retention rate after heat treatment at 800℃ for 1h is 80.3%.

[0093] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0094] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-cost preparation method for a silicon-calcium based aerogel material, characterized in that, The process includes the following steps: sol-gel, impurity washing, high-temperature aging, and microwave drying; The sol-gel method involves adjusting the pH of the silicon source solution to 4-6 using an acidic catalyst, then mixing it evenly with a calcium source solution to obtain a silicon-calcium sol; the silicon-calcium sol is then allowed to stand and gel to obtain a silicon-calcium gel. The silicon source used in the silicon source solution is liquid water glass; the silicon dioxide content in the liquid water glass is >25%, and the modulus is >3.0; the calcium source used in the calcium source solution is one of the following: calcium chloride, calcium nitrate, calcium formate, calcium acetate, or calcium lactate; No organic solvents are used in the sol-gel; The method for washing away the impurities is to wash the calcium silicate gel with deionized water; The high-temperature aging method is as follows: the washed calcium silicate gel is placed in deionized water, and in a closed environment, the aging temperature is controlled at 180-300℃ and the aging pressure is 8.5-10MPa. After the high-temperature aging treatment is carried out for 12-24 hours with heat and pressure, the preform is obtained. During the high-temperature aging process, the volume ratio of the washed calcium silicate gel to deionized water is 1:1-2. The microwave processing method is as follows: control the microwave frequency to 2400-2500MHz, and sequentially perform a first microwave drying treatment, a second microwave drying treatment, and a third microwave drying treatment on the preform to obtain calcium-silicon-based aerogel. In the first microwave drying process, the microwave power density is controlled at 3.5-4 W / g, the microwave drying temperature is 100-105℃, and the microwave drying time is 10-15 min. In the second microwave drying process, the microwave power density is controlled at 2.5-3 W / g, the microwave drying temperature is 120-125℃, and the microwave drying time is 40-50 min. In the third microwave drying process, the microwave power density is controlled at 1.8-2.2 W / g, the microwave drying temperature is 135-140℃, and the microwave drying time is 10-20 min.

2. The low-cost preparation method of the silicon-calcium based aerogel material according to claim 1, characterized in that, In the sol-gel process, the temperature of the gel during static storage is 50-70℃, and the relative humidity is not less than 90%. The gel should be allowed to stand for 0.5-1 hour.

3. The low-cost preparation method of the silicon-calcium based aerogel material according to claim 1, characterized in that, In the sol-gel, the hydrogen ion concentration in the acidic catalyst is 1-3 mol / L, and the acidic catalyst is one of the following: hydrochloric acid, nitric acid, formic acid, acetic acid, or lactic acid.

4. The low-cost preparation method of the silicon-calcium based aerogel material according to claim 1, characterized in that, In the sol-gel, the volume ratio of silicon source to deionized water in the silicon source solution is 1:1-3; The CaO content in the calcium source solution is 5-30 wt%; The mixing of silicon source solution and calcium source solution must meet the following requirements: the molar ratio of SiO2 in silicon source solution to CaO in calcium source solution is 1-3:

1.

5. The low-cost preparation method of the silicon-calcium based aerogel material according to claim 1, characterized in that, In the impurity washing process, the volume ratio of silica-calcium gel to deionized water is 1:3-5. Deionized water should be changed every 8-12 hours, for a total of 3-4 times.

6. A silica-calcium-based aerogel product prepared by the method according to any one of claims 1-5.