Preparation method of chemical phase change aerogel heat insulation composite material

Abstract

The invention relates to the technical field of phase change composite materials, in particular to a chemical phase change aerogel heat insulation composite material and a preparation method thereof. According to the specific technical scheme, the preparation method comprises the following steps: (1) adding a silane precursor into an ethanol water solution, adding an acidic catalyst for hydrolysis for 1-4 hours, adding nano manganese dioxide, stirring for 10-60 minutes, performing ultrasonic treatment for 10-30 minutes, and then adding alkali to adjust the pH value of sol to 7-10; (2) permeating the sol mixed in the step (1) into the needled fiber felt, wherein the vacuum impregnation time is 1-120 minutes; and (3) aging the gel prepared in the step (2), replacing with an ethanol solvent, and finally carrying out carbon dioxide supercritical drying to obtain the composite material. The invention provides a chemical phase change heat insulation strategy, and the prepared chemical phase change aerogel heat insulation composite material is simple in preparation process, has excellent heat insulation performance in both high-temperature and low-temperature environments, is high in phase change enthalpy value, can be effectively decomposed and absorb heat under high-heat flow, has excellent heat radiation blocking performance, and can be used as a heat insulation material. The influence caused by high-temperature heat radiation can be effectively resisted, the double advantages of the phase change material and the aerogel are integrated, and good application prospects are achieved in the field of high-temperature heat insulation.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change composite materials, and particularly to a preparation method of a chemical phase change aerogel thermal insulation composite material. Background Art

[0002] Currently, phase change materials are mainly applied in the field of low-temperature phase change, used for storing and releasing heat to regulate temperature fluctuations. These materials have been widely used in fields such as building insulation, heat dissipation of electronic devices, and solar energy utilization. Phase change materials have the characteristic of high heat storage density while maintaining the temperature almost constant. Whether it is in the heat dissipation protection of electronic devices, building insulation, or thermal management of textiles, phase change materials can play an important role. These materials achieve effective storage and release of energy by absorbing or releasing heat during the phase change process, while keeping the temperature basically stable. The application of phase change materials extends the constant temperature time and significantly improves the thermal insulation protection effect. However, existing phase change materials such as molten salts and metal phase change materials, from the perspective of chemical principles, may produce corrosive substances after decomposition. Once these corrosive substances come into contact with surrounding materials or equipment, corrosion will occur.

[0003] In traditional applications, phase change material composite aerogels are mainly used in low-temperature fields, and in some cases, their thermal conductivity is deliberately increased to facilitate rapid absorption and release of heat. However, in the aerospace field, especially in the face of high-temperature environments, this design concept needs to be significantly adjusted. High-temperature phase change materials used in the aerospace field must be able to maintain stability and a low heat transfer rate under extreme temperature conditions. In this context, reducing the thermal conductivity becomes crucial. Therefore, for high-temperature phase change materials in the aerospace field, researchers are committed to developing phase change composite materials with lower thermal conductivity. These new materials can provide more reliable thermal insulation protection in high-temperature environments, can resist thermal shock, ensure the safe operation and precise control of spacecraft, and play a role in passive thermal management and thermal protection in aerospace.

[0004] At present, the phase change processes of the vast majority of phase change materials are solid-liquid phase changes, and this inherent characteristic has led to a series of problems. During the solid-liquid phase change process, the phase change materials are extremely prone to leakage. In many application scenarios, such as in thermal management systems and energy storage systems, the phase change materials achieve heat storage and release by virtue of their unique phase change characteristics. However, due to the physical state change of the materials during the solid-liquid phase change, it is difficult to maintain their stability. This leakage problem will not only interfere with the normal function of the phase change materials in the system, reduce their energy conversion and storage efficiency, but also may have adverse reactions with other components in the system. The material design, microstructure regulation or new encapsulation technology of the phase change materials will bring troublesome preparation processes and complex practical application difficulties. Therefore, the development of new phase change materials has become an urgent task, and it is necessary to break through the framework of traditional solid-liquid phase change materials, search for new material systems or innovative structural designs, so as to create new phase change materials that not only have high phase change performance but also can avoid leakage risks. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a preparation method of a chemically phase-changing aerogel thermal insulation composite material.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0007] The present invention discloses a preparation method of a chemically phase-changing aerogel thermal insulation composite material, including the following steps:

[0008] (1) Add a silane precursor to a mixed solution of water or ethanol and water, add an acidic catalyst to adjust the pH to 2-5, and hydrolyze for 1-4 h. Then add nano-manganese dioxide, stir for 10-60 min and ultrasonicate for 10-30 min, and then add a base to adjust the pH of the sol to 7-10;

[0009] (2) Permeate the sol prepared in step (1) into a needled fiber felt, and the vacuum impregnation time is 1-120 min;

[0010] (3) Age the gel prepared in step (2) and replace it with an ethanol solvent, and finally perform supercritical carbon dioxide drying to obtain the composite material.

[0011] Preferably, in step (1), the silane precursor is at least one of tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane; the acid catalyst is at least one of acetic acid, hydrochloric acid, nitric acid, sulfuric acid; the base is at least one of ammonia water, sodium hydroxide, potassium hydroxide.

[0012] Preferably, the molar ratio of the silane precursor: water: ethanol is 1:1 to 30:0 to 10; the nano manganese dioxide accounts for 5% to 75% of the total mass of the mixed sol, and the sol after hydrolysis of the silane precursor accounts for 25% to 95% of the total mass of the mixed sol.

[0013] Preferably, in step (2), the needled fiber felt is a silica fiber felt, an alumina fiber felt, a mullite fiber felt, a zirconia fiber felt, a silicon carbide fiber felt, a boron nitride fiber felt or a mixed fiber felt of several of them.

[0014] Preferably, in step (3), the aging liquid is an ethanol aqueous solution, the volume ratio of water: ethanol in the aging liquid formulation is 1:1 to 4, and the aging time is 1 h to 4 d.

[0015] Preferably, in step (1), the preparation process of the nano manganese dioxide is as follows: after mixing an aqueous manganese salt solution and an aqueous potassium permanganate solution, stir and react, centrifuge 3 to 6 times, and take the lower layer precipitate to obtain nano manganese dioxide.

[0016] Preferably, the manganese salt is any one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride.

[0017] Preferably, the molar ratio of manganese salt: water for manganese salt solution: potassium permanganate: water for potassium permanganate solution is 0.03 to 0.24: 2.5 to 3: 0.01 to 0.08: 2.5 to 3.

[0018] Preferably, the stirring temperature is 30 to 80 °C, and the stirring time is 0.5 to 6 h.

[0019] Correspondingly, a chemical phase change aerogel thermal insulation composite material prepared by the above preparation method.

[0020] The present invention has the following beneficial effects:

[0021] 1) The present invention introduces a chemical phase change function: by adding nano manganese dioxide and utilizing its characteristic of endothermic decomposition at a specific temperature, a large amount of heat can be absorbed, providing a new solution for high-temperature thermal insulation. Moreover, manganese dioxide has good compatibility with silica, ensuring that the original structure of the aerogel is not damaged and maintaining the physical properties of the material stable.

[0022] 2) Controllability of pore size and porosity: By finely regulating the ratio of the silane precursor and the solvent, the pore size and porosity inside the aerogel can be effectively controlled, and then the specific surface area and thermal conductivity of the material can be adjusted. This controllability enables the aerogel to have broader application potential in the fields of thermal insulation materials and thermal insulation.

[0023] 3) Improve the resistance to the thermal radiation coefficient: The addition of nano-manganese dioxide improves the thermal radiation absorption and reflectivity of the composite material, effectively resists the influence of thermal radiation in the high-temperature range, and further improves the heat insulation performance of the material. Description of the Drawings

[0024] Figure 1 It is the microscopic morphology diagram (left) of γ-MnO2 prepared in Example 1 and the microscopic morphology diagram (right) of α-MnO2 obtained in Example 3;

[0025] Figure 2 It is the macroscopic and microscopic morphology diagrams of the composite material prepared in Example 1; (A) is the macroscopic morphology diagram, and (B)(C) are the microscopic morphology diagrams;

[0026] Figure 3 It is the DSC curves of the composite materials prepared in Example 1 and Example 2;

[0027] Figure 4 It is the back temperature curve of the composite material prepared in Example 1 when facing a heat flux of 1000 °C;

[0028] Figure 5 It is the infrared reflectivity curve of the composite material prepared in Example 1 and the infrared reflectivity curve of pure silica aerogel. Detailed Embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0031] Based on the lack of high-temperature phase change materials in the current aerospace field, the present invention provides a brand-new solution, that is: by adjusting the ratio of silane precursor and solvent, changing the size of silica particles and silica clusters inside the aerogel, and realizing the adjustment of pore size, porosity and specific surface area, thereby controlling the thermal conductivity of silica-based aerogel. At the same time, by adding nano-manganese dioxide to introduce chemical phase change function into the aerogel, the added manganese dioxide does not chemically react with silica, does not damage the original aerogel structure, and decomposes and absorbs a large amount of heat at the phase change point. In addition, by adding nano-manganese dioxide, the weak thermal radiation blocking performance of silica aerogel is improved, the high-temperature thermal conductivity is greatly reduced, and the high-temperature heat insulation effect is remarkable. By means of supercritical carbon dioxide, while removing ethanol in the composite material, it does not damage the microstructure of the aerogel and does not affect the phase change function of manganese dioxide.

[0032] The preparation method of the chemically phase-changing aerogel thermal insulation composite material disclosed by the present invention specifically includes the following steps:

[0033] (1) Dissolve manganese salt and potassium permanganate in water respectively to form aqueous solutions, then add the manganese salt aqueous solution to the potassium permanganate aqueous solution, stir and react at an appropriate temperature, and then centrifuge 3-6 times in a centrifuge tube, and take the lower layer precipitate, which is nano-manganese dioxide. Among them, the manganese salt is any one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride. The molar ratio of manganese salt: water for manganese salt solution: potassium permanganate: water for potassium permanganate solution is 0.03-0.24: 2.5-3: 0.01-0.08: 2.5-3, the stirring temperature is 30-80 °C, and the stirring time is 0.5-6 h.

[0034] (2) Add the silane precursor to water or a mixed solution of ethanol and water, and add an acidic catalyst to adjust the pH to 2-5 for hydrolysis for 1-4 h. Then add the nano-manganese dioxide prepared in step (1) to the hydrolyzed sol, stir for 10-60 min and ultrasonicate for 10-30 min to ensure uniform distribution of components, and then add an alkali to adjust the pH of the sol to 7-10.

[0035] Among them, the silane precursor is at least one of tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, and diethyldiethoxysilane; the acid catalyst is at least one of acetic acid, hydrochloric acid, nitric acid, and sulfuric acid; the alkali is at least one of ammonia water, sodium hydroxide, and potassium hydroxide.

[0036] The molar ratio of silane precursor: water: ethanol is 1:1 to 30:0 to 10; nano manganese dioxide accounts for 5% to 75% of the total mass of the mixed sol, and the sol after hydrolysis of the silane precursor accounts for 25% to 95% of the total mass of the mixed sol. The mixed sol here refers to the sum of manganese dioxide and the sol after hydrolysis.

[0037] As another embodiment, in addition to using α-MnO2, β-MnO2, γ-MnO2, δ-MnO2 prepared in step (1), manganese dioxide can also be obtained by purchase.

[0038] (3) The mixed sol in step (2) is infiltrated into the needle-punched fiber felt by vacuum impregnation, and the vacuum impregnation time is 1 to 120 min; the needle-punched fiber felt can be a silica fiber felt, an alumina fiber felt, a mullite fiber felt, a zirconia fiber felt, a silicon carbide fiber felt, a boron nitride fiber felt, or a mixed fiber felt of several of them.

[0039] (4) The gel is aged under appropriate conditions and replaced with an ethanol solvent. The ethanol concentration is 75% - absolute ethanol. The composite material is immersed for solvent replacement, and finally supercritical carbon dioxide drying is carried out to obtain the composite material. The aging solution is an ethanol aqueous solution, the volume ratio of water: ethanol in the aging solution is 1:1 to 4, and the aging time is 1 h to 4 d.

[0040] The present invention will be further described below in conjunction with specific embodiments.

[0041] Example 1

[0042] The preparation process of the chemical phase change aerogel thermal insulation composite material is as follows:

[0043] (1) 9.06 g of anhydrous manganese sulfate and 3.16 g of potassium permanganate are respectively dissolved in 100 ml of water and stirred to form an aqueous solution. Then the manganese sulfate solution is added to the potassium permanganate aqueous solution, stirred at 40 °C for 2 h, and then centrifuged 3 times in a centrifuge tube. The lower layer precipitate is taken as the subsequent manganese dioxide material (γ-MnO2), and its morphology is shown in Figure 1 the left side view.

[0044] (2) 20.8 g of tetraethyl orthosilicate is added to a mixed solution of 10.8 g of water and 20.16 g of ethanol, and 0.5 g of 0.12 mol / L dilute hydrochloric acid is added to adjust the pH = 3 for hydrolysis for 2 h. Then the nano manganese dioxide prepared in step 1 is added to the hydrolyzed sol, stirred for 30 min and ultrasonically treated for 15 min to ensure uniform distribution of the components. Then ammonia water is added to adjust the pH of the sol to 8.

[0045] (3) The mixed sol is infiltrated into the silica fiber felt by vacuum impregnation, and the vacuum impregnation time is 60 min.

[0046] (4) adding an aging solution with a volume ratio of water to ethanol = 1:1 at room temperature (20°C to 30°C) for 2 days to age the gel, then performing solvent replacement with ethanol for 2 days, and finally performing supercritical carbon dioxide drying to obtain a composite material.

[0047] The macroscopic and microscopic morphologies of the composite material prepared in Example 1 are as follows: Figure 2 As shown, from Figure 2 It can be seen that the composite fibers and aerogel are tightly bonded and the nano-skeleton is evenly distributed.

[0048] The infrared reflectivity curve of the composite material prepared in Example 1 and the infrared reflectivity curve of pure silica aerogel are as follows: Figure 5 As shown, it can be seen that the material prepared in Example 1 has a higher infrared reflectivity.

[0049] Taking pure silica aerogel as a control, the back temperature curve of the prepared composite material when facing a 1000℃ heat flow is as follows: Figure 4 As shown, the results show that the performance of the composite material is better than that of pure silica aerogel composite material.

[0050] Example 2

[0051] The preparation process of chemical phase change aerogel thermal insulation composite material is as follows:

[0052] (1) 10.74 g of anhydrous manganese nitrate and 3.16 g of potassium permanganate were dissolved in 100 ml of water and stirred to form an aqueous solution, and then the manganese nitrate solution was added to the potassium permanganate aqueous solution, stirred at 40° C. for 2 h, and then centrifuged in a centrifuge tube for 3 times, and the lower precipitate was taken as the subsequent manganese dioxide material.

[0053] (2) 10.4 g of ethyl orthosilicate was added to a mixed solution of 5.4 g of water and 10.08 g of ethanol, and 0.5 g of 0.12 mol / L dilute hydrochloric acid was added to adjust the pH to 3 for hydrolysis for 2 h, and then the nano manganese dioxide prepared in step 1 was added to the hydrolyzed sol, stirred for 30 min and ultrasonicated for 15 min to ensure uniform distribution of the components, and then ammonia water was added to adjust the pH of the sol to 8;

[0054] (3) infiltrating the mixed sol into the silica fiber felt by vacuum impregnation for 60 min;

[0055] (4) adding an aging solution with a volume ratio of water to ethanol = 3:2 and aging at 40° C. for 2 days, then using ethanol for solvent replacement for 2 days, and finally performing carbon dioxide supercritical drying to obtain a composite material.

[0056] The DSC curves of the composite materials prepared in Example 1 and Example 2 are shown in Figure 3As shown, the results show that the composite material has an endothermic effect of chemical phase change, and the highest enthalpy value is 132 j / g.

[0057] Example 3

[0058] The preparation process of the chemical phase change aerogel thermal insulation composite material is as follows:

[0059] (1) Dissolve 4.53 anhydrous manganese sulfate and 1.58 g of potassium permanganate in 50 ml of water respectively and stir to form aqueous solutions. Then add the manganese nitrate solution to the potassium permanganate aqueous solution, stir at 40 °C for 2 h, and then centrifuge 3 times in a centrifuge tube. Take the lower layer precipitate as the subsequent manganese dioxide material (α-MnO2), and its morphology is shown in Figure 1 the right view shown. The results show that by changing the reactant concentration, the crystal phase and microstructure of manganese dioxide can be changed.

[0060] (2) Add 20.8 g of tetraethyl orthosilicate to a mixed solution of 10.8 g of water and 20.16 g of ethanol, and add 0.5 g of 0.12 mol / L dilute hydrochloric acid to adjust the pH = 3. After hydrolysis for 2 h, add the nano-manganese dioxide prepared in step 1 to the hydrolyzed sol, stir for 30 min and ultrasonicate for 15 min to ensure uniform distribution of components, and then add ammonia water to adjust the pH of the sol to 8.

[0061] (3) The mixed sol is infiltrated into the silica fiber felt by vacuum impregnation, and the vacuum impregnation time is 60 min.

[0062] (4) Add an aging solution with a water:ethanol volume ratio of 1:1, age at 40 °C for 2 d, then perform solvent replacement with ethanol for 2 d, and finally perform supercritical carbon dioxide drying to obtain the composite material.

[0063] Example 4

[0064] According to the preparation methods disclosed in Example 1 and Example 2, by changing the addition amounts of manganese nitrate and manganese sulfate and the alcohol-water ratio, the mesoporous specific surface area, pore volume and average pore diameter of the prepared composite materials are shown in Table 1 below. The results show that by adjusting the preparation parameters, composite materials with different pore structures can be obtained.

[0065] Table 1 Mesoporous specific surface area, pore volume and average pore diameter of composite materials prepared under different conditions

[0066]

[0067] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of a chemical phase change aerogel thermal insulation composite material, characterized in that: It includes the following steps: (1) Add a silane precursor to a mixed solution of water or ethanol and water. After adding an acidic catalyst to adjust the pH to 2-5 and hydrolyzing for 1-4 h, add nano-manganese dioxide, stir for 10-60 min and ultrasonicate for 10-30 min, and then add an alkali to adjust the pH of the sol to 7-10; (2) Impregnate the sol prepared in step (1) into the needle-punched fiber felt, and the vacuum impregnation time is 1-120 min; (3) Age the gel prepared in step (2) and replace it with an ethanol solvent, and finally perform supercritical carbon dioxide drying to obtain the composite material.

2. The preparation method according to claim 1, characterized in that: In step (1), the silane precursor is tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane; the acid catalyst is at least one of acetic acid, hydrochloric acid, nitric acid, and sulfuric acid; the alkali is at least one of ammonia water, sodium hydroxide, and potassium hydroxide.

3. The preparation method according to claim 2, characterized in that: The molar ratio of silane precursor: water: ethanol is 1:1-30:0-10; nano-manganese dioxide accounts for 5%-75% of the total mass of the mixed sol, and the sol after hydrolysis of the silane precursor accounts for 25%-95% of the total mass of the mixed sol.

4. The preparation method according to claim 1, characterized in that: In step (2), the needle-punched fiber felt is a silica fiber felt, an alumina fiber felt, a mullite fiber felt, a zirconia fiber felt, a silicon carbide fiber felt, a boron nitride fiber felt, or a mixed fiber felt of several of them.

5. The preparation method according to claim 1, characterized in that: In step (3), the aging solution is an ethanol aqueous solution, the volume ratio of water to ethanol in the aging solution is 1:1-4, and the aging time is 1 h-4 d.

6. The preparation method according to claim 1, characterized in that: In step (1), the preparation process of nano-manganese dioxide is as follows: Mix an aqueous manganese salt solution and an aqueous potassium permanganate solution, stir and react, centrifuge 3-6 times, and take the lower layer precipitate to obtain nano-manganese dioxide.

7. The preparation method according to claim 6, characterized in that: The manganese salt is any one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride.

8. The preparation method according to claim 6 or 7, characterized in that: The molar ratio of manganese salt: water for manganese salt solution: potassium permanganate: water for potassium permanganate solution is 0.03-0.24:2.5-3:0.01-0.08:2.5-3.

9. The preparation method according to claim 8, characterized in that: The stirring temperature is 30-80 °C, and the stirring time is 0.5-6 h.

10. A chemically phase-changing aerogel thermal insulation composite material prepared by the preparation method according to any one of claims 1-9.

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