A method for preparing a carbon-based aerogel composite material with low infrared emissivity

Abstract

The application discloses a preparation method of a carbon-based aerogel composite material with low infrared emissivity, and specifically comprises the following steps: dissolving m-trimesic acid in ethanol to obtain solution A; dissolving Cu(NO3)2*3H2O in water to obtain solution B; adding solution B into solution A and reacting at high temperature to obtain a copper MOF precursor with a regular octahedron structure; carbonizing the precursor at high temperature and under N2, and then performing a sulfuration reaction with a sulfur source at high temperature and under N2 to obtain CuS-MOF with a regular octahedron structure; dispersing the product in water to obtain solution C; dispersing sodium molybdate and L-cysteine in water to obtain solution D; mixing solution C and solution D and then reacting at high temperature to obtain CuS / MoS2-MOF with a regular octahedron structure; dissolving the product and sodium alginate in water, stirring uniformly, adding acetic acid into the solution to form a hydrogel, and freeze-drying the hydrogel to obtain the aerogel.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a carbon-based aerogel composite material with low infrared emissivity. BACKGROUND

[0002] In order to reduce the probability of being detected by an infrared detection system, more and more infrared stealth materials are being developed and utilized. According to the principle of infrared detection, two important conditions for infrared stealth are emissivity and temperature. Low emissivity can suppress or reduce the infrared radiation intensity of the target, change the shape and pattern of the target in the infrared thermal image, and reduce the probability of being discovered. Low infrared emissivity material technology has the advantages of significant reduction of infrared radiation, small weight increase of equipment, no change of the shape and structure of the equipment during use, etc., making it an important technical approach for equipment infrared stealth. At the same time, passive measures such as installing thermal insulation materials on the outside of the target or surface cooling can indirectly separate the high temperature generated by the target, thereby suppressing infrared radiation, which is also an important way to achieve infrared stealth.

[0003] Zhu et al. prepared nanopillar crystalline ITO thin films by radio frequency magnetron sputtering. According to the analysis, the nanopillar crystalline thin film shows (400) preferred orientation, and the increase in the number of carriers causes the change of the energy band gap, which in turn affects the emissivity of the thin film in the infrared band. The thin film deposited at 200 W shows the best optical and electrical properties, with a resistivity of 1.44 x 10 -4 Ω·cm, and an infrared emissivity of only 0.112. (Dong L, Zhu G S, Xu H R, Jiang X P, Zhang X Y, Zhao YY, Yan D L, Yuan L, Yu AB; (Fabrication of Nanopillar Crystalline ITO Thin Films with High Transmittance and IR Reflectance by RF Magnetron Sputtering, Materials (2019) 12(6) 958). However, the above-mentioned material does not consider the thermal insulation performance of the material, and it is not enough to achieve good infrared stealth effect only by low infrared reflectivity. Poor thermal insulation performance will still lead to poor infrared stealth effect in application. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a carbon-based aerogel composite material with low infrared emissivity and good thermal insulation performance.

[0005] Technical solution: The preparation method of the carbon-based aerogel composite material with low infrared emissivity according to the present application comprises the following steps:

[0006] (1) preparing a copper MOF precursor: dissolving trimesic acid in ethanol to obtain solution A; dissolving Cu(NO3)2·3H2O in water to obtain solution B; adding solution B to solution A, mixing and reacting at high temperature, and then washing and drying the product to obtain a copper MOF precursor with a regular octahedral structure;

[0007] (2) carbonizing the precursor at high temperature and under N2, and then sulfidizing the carbonized product with a sulfur source at high temperature and under N2, so that Cu on the skeleton is sulfidized into CuS to obtain a CuS-MOF with a regular octahedral structure;

[0008] (3) dispersing the product of step (2) in water to obtain solution C; dispersing sodium molybdate and L-cysteine in water to obtain solution D; mixing solution C and solution D, and then reacting at high temperature, so that MoS2 grows on the CuS site of the skeleton to form a CuS / MoS2 composite; and obtaining a CuS / MoS2-MOF with a regular octahedral structure;

[0009] (4) dissolving the product of step (3) and sodium alginate in water, stirring, and then adding acetic acid to the solution to form a hydrogel, and freeze-drying the hydrogel to obtain a porous aerogel.

[0010] In step (1), the molar ratio of trimesic acid to Cu(NO3)2·3H2O is 5:9-10.

[0011] In step (1), the reaction temperature is 120-125℃, and the reaction time is not higher than 10h; the drying temperature is 60-65℃, and the drying time is not less than 24h.

[0012] In step (2), the carbonization temperature is 550-600℃, and the carbonization time is 1-2h; the sulfidization temperature is 345-350℃, and the sulfidization time is 2.5-3h.

[0013] In step (2), during the sulfidization process, the sulfur source is sulfur powder; the precursor powder and the sulfur powder are placed in a tube furnace, the mass ratio of the precursor powder to the sulfur powder is 1:2, the sulfur powder is placed upstream, and the precursor powder is placed downstream along the nitrogen flow direction.

[0014] In step (3), the mixed molar ratio of sodium molybdate to L-cysteine is 1:4.

[0015] In step (3), the reaction temperature is 200-250℃, and the reaction time is 14-15h.

[0016] In step (4), the pore size of the pore structure in the porous aerogel is 10-300 mu m. The aerogel composite has high porosity, and thus has good heat insulation performance. The surface temperature remains low within 120 s of heating time.

[0017] When the infrared detection wave is incident on the surface of the material, due to the presence of transition metal sulfide (CuS and MoS2), surface plasmon resonance absorption is generated in the near-infrared region, thereby reducing the infrared emissivity of the material; at the same time, due to the porous structure of the aerogel, a large amount of air is contained inside, and the thermal conductivity of air is very low, thereby keeping the surface of the material at a low temperature, and further reducing the infrared radiation energy.

[0018] Advantages: Compared with the prior art, the present application has the following advantages: (1) the low infrared emissivity aerogel of the present application is composed of carbon-based materials and transition metal sulfides. When infrared detection is performed, due to the presence of transition metal sulfides inside, surface plasmon resonance absorption is generated in the near-infrared region, thereby having low infrared emissivity, and the infrared emissivity in the 8-14 mu m band is 0.62; (2) due to the rich pore structure of the aerogel, the aerogel has good heat insulation performance, and the surface of the material remains low (37.2 DEG C) within 120 s of heating time, effectively reducing the infrared radiation energy, so that the infrared thermal imaging instrument cannot present a clear and detectable target when the aerogel is applied, and good infrared stealth effect is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Scanning electron microscope image of the copper MOF prepared in step (1) of Example 1;

[0020] Figure 2 Scanning electron microscope image of the CuS / MoS2-MOF prepared in step (3) of Example 1;

[0021] Figure 3 XPS image of the CuS / MoS2-MOF prepared in step (3) of Example 1;

[0022] Figure 4 XRD image of the CuS / MoS2-MOF prepared in step (3) of Example 1;

[0023] Figure 5 Scanning electron microscope image of the aerogel prepared in Example 1;

[0024] Figure 6 Infrared emissivity comparison of different materials;

[0025] Figure 7 Heat insulation performance of the aerogel prepared in Example 1;

[0026] Table 1 shows the thermal insulation performance data of aerogels under different heating times. Detailed Implementation

[0027] Example 1

[0028] The present invention provides a method for preparing a carbon-based aerogel composite material with low infrared emissivity, comprising the following steps:

[0029] (1) Preparation of copper MOF precursor: 2.5 × 10 -3 1 mol of tribenzoic acid was dissolved in 15 mL of ethanol by sonication to obtain solution A; 4.5 × 10 -3 mol Cu(NO3)2·3H2O was dissolved in 15 mL of deionized water to obtain solution B; solution B was added to solution A, stirred for 20 min, and then transferred to a reaction vessel and reacted at 120 °C for 10 h. After the reaction, the product was centrifuged and washed alternately with deionized water and ethanol, and then dried at 60 °C for 24 h to obtain a dark blue powder; the microstructure of the product is a copper MOF with a regular octahedral structure.

[0030] (2) The dark blue powder was carbonized at 600℃ and under N2 for 2 hours to obtain Cu@N black powder; then the Cu@N black powder and sulfur powder were placed in a tube furnace at a mass ratio of 1:2, with sulfur powder placed upstream and Cu@N black powder placed downstream along the direction of nitrogen flow; the tube furnace was heated to 350℃ and heated under N2 for 3 hours; finally, it was cooled to room temperature and the black powder CuS@N was collected; the microstructure of the product was CuS-MOF with a regular octahedral structure, and the Cu on the framework was sulfided into CuS after sulfidation.

[0031] (3) Disperse the black powder CuS@N (1 mmol) from step (2) in deionized water to obtain solution C; disperse 1 mmol sodium molybdate and 4 mmol L-cysteine ​​in 35 mL deionized water (sodium molybdate (Na2MoO4.2H2O) and L-cysteine ​​(C3H7NO2S) can generate MoS2) to obtain solution D; stir solutions C and D evenly and put them into a reaction vessel, react at 200℃ for 14 h, wash the product by centrifugation and dry it at 60℃, and collect the black powder CuS / MoS2; MoS2 grows at the CuS sites in the framework to form CuS / MoS2 complex, and the microstructure of the product is CuS / MoS2-MOF with a regular octahedral structure;

[0032] (4) Preparation of aerogel: The black powder prepared in step (3) and sodium alginate are dissolved in deionized water at a mass ratio of 1:2. After stirring evenly, 10 μL of acetic acid is added to the solution to form a hydrogel. The hydrogel is placed in a mold and freeze-dried to obtain a porous aerogel.

[0033] Comparative Example 1

[0034] A method for preparing a carbon-based aerogel includes the following steps:

[0035] (1) Preparation of copper MOF precursor: 2.5 × 10 -3 1 mol of tribenzoic acid was dissolved in 15 mL of ethanol by sonication to obtain solution A; 4.5 × 10 -3 mol Cu(NO3)2·3H2O was dissolved in 15 mL of deionized water to obtain solution B; solution B was added to solution A, stirred for 20 min, and then transferred to a reaction vessel and reacted at 120 °C for 10 h. After the reaction, the product was centrifuged and washed alternately with deionized water and ethanol, and then dried at 60 °C for 24 h to obtain a dark blue powder; the microstructure of the product is a copper MOF with a regular octahedral structure.

[0036] (2) Preparation of aerogel: Dissolve the dark blue powder and sodium alginate in deionized water at a mass ratio of 1:2 in step (1), stir evenly, and then add 10 μL of acetic acid to the solution to form a hydrogel. Place the hydrogel in a mold and freeze dry to obtain a porous aerogel.

[0037] from Figure 1 As can be seen, the prepared copper MOF precursor has a regular octahedral structure. Each regular octahedral structure is stable and suitable for Cu on the framework to be sulfided into CuS to form a CuS-MOF framework.

[0038] from Figure 2 It can be seen that MoS2 was successfully grown on the CuS-MOF framework, which is beneficial to reducing the infrared emissivity of the material.

[0039] from Figure 3 The spectrum reveals the composition and valence states of different elements. The Cu2p spectrum has two peaks near 951.9 and 932 eV; the Mo3d spectrum has two peaks near 228.8 and 231.8 eV; and the S2p peaks are the spin orbitals. 1 / 2 and S2p 3 / 2 Composition; this facilitates plasma vibration absorption in the near-infrared region, thereby reducing the infrared emissivity of the material.

[0040] from Figure 4The diffraction peaks at 2θ = 27.7°, 29.3°, 31.8°, 39.9°, 47.9°, 52.7°, and 58.8° correspond to the (101)(102)(103)(006)(1 10)(108) and (1 16) diffraction peaks at 2θ = 14.6°, 31.8°, 39.8°, and 58.8°, respectively. The (0 0 2), (1 0 0), (1 0 3), and (1 1 0) peaks at 2θ = 14.6°, 31.8°, 39.8°, and 58.8° agree well with the standard spectrum of MoS2, indicating that CuS and MoS2 coexist.

[0041] from Figure 5 As can be seen, aerogels have a rich pore structure with varying pore sizes, ranging from 10μm to 300μm. Aerogels can store a large amount of air inside, which is beneficial for improving the thermal insulation performance of the material and reducing the infrared radiation energy of the target.

[0042] Figure 6 To compare the infrared emissivity of different materials, from Figure 5 As can be seen, when the material is only the aerogel prepared by the copper MOF in step (1) (i.e., Comparative Example 1), the emissivity is very high, reaching 0.94; while the emissivity of the aerogel material formed by the final CuS / MoS2-MOF is significantly reduced, only 0.62.

[0043] from Figure 7 As can be seen, on the heating platform, after heating for 120 seconds, when the platform temperature reaches 126.2℃, the aerogel surface still maintains a low temperature (37.2℃). This indicates that when the aerogel material of this invention is used on the surface of equipment, even if the equipment temperature rises after use, the equipment surface can still maintain a low temperature due to the aerogel material of this invention covering it, thereby reducing the external infrared radiation energy and achieving the effect of infrared stealth.

[0044] Table 1

[0045]

[0046]

[0047] As shown in Table 1, the temperature of the aerogel surface remained lower than the background temperature at different heating times. This indicates that when the aerogel material of this invention is used to cover the equipment surface, even if the equipment temperature rises after use, the equipment surface can still maintain a low temperature, thereby reducing the outward infrared radiation energy and achieving the effect of infrared stealth.

Claims

1. A method for preparing a carbon-based aerogel composite material with low infrared emissivity, characterized in that, Includes the following steps: (1) Preparation of copper MOF precursor: Tribenzoic acid was dissolved in ethanol to obtain solution A; Cu(NO3)2·3H2O was dissolved in water to obtain solution B; solution B was added to solution A, mixed and reacted at high temperature; the product after reaction was washed and dried to obtain copper MOF precursor with regular octahedral structure. (2) The precursor is carbonized under high temperature and N2 conditions, and then sulfidation reaction is carried out with sulfur source under high temperature and N2 conditions. After sulfidation, Cu on the framework is sulfidated into CuS, and CuS-MOF with regular octahedral structure is obtained. (3) Disperse the product of step (2) in water to obtain solution C; disperse sodium molybdate and L-cysteine ​​in water to obtain solution D; mix solution C and solution D and react at high temperature. After the reaction, MoS2 grows on the CuS site of the framework to form CuS / MoS2 complex; obtain CuS / MoS2-MOF with regular octahedral structure. (4) Dissolve the product of step (3) and sodium alginate in water, stir well, add acetic acid to the solution to form a hydrogel, and freeze-dry the hydrogel to obtain a porous aerogel.

2. The method for preparing a carbon-based aerogel composite material with low infrared emissivity according to claim 1, characterized in that: In step (1), the molar ratio of tribenzoic acid to Cu(NO3)2·3H2O is 5:9-10.

3. The method for preparing a carbon-based aerogel composite material with low infrared emissivity according to claim 1, characterized in that: In step (1), the reaction temperature is 120-125℃ and the reaction time is no more than 10h; the drying temperature is 60-65℃ and the drying time is no less than 24h.

4. The method for preparing a carbon-based aerogel composite material with low infrared emissivity according to claim 1, characterized in that: In step (2), the carbonization temperature is 550-600℃ and the carbonization time is 1-2h; the sulfidation temperature is 345-350℃ and the sulfidation time is 2.5-3h.

5. The method for preparing a carbon-based aerogel composite material with low infrared emissivity according to claim 1, characterized in that: In step (2), during the sulfidation process, the sulfur source is sulfur powder; the precursor powder and sulfur powder are placed in a tube furnace with a mass ratio of 1:

2. Along the direction of nitrogen flow, sulfur powder is placed upstream and precursor powder is placed downstream.

6. The method for preparing a carbon-based aerogel composite material with low infrared emissivity according to claim 1, characterized in that: In step (3), the molar ratio of sodium molybdate and L-cysteine ​​is 1:

4.

7. The method for preparing a carbon-based aerogel composite material with low infrared emissivity according to claim 1, characterized in that: In step (3), the reaction temperature is 200-250℃ and the reaction time is 14-15h.

8. The method for preparing a carbon-based aerogel composite material with low infrared emissivity according to claim 1, characterized in that: In step (4), the pore size of the porous aerogel is 10 μm to 300 μm.

Images