Preparation method of carbon-based aerogel composite material with strong infrared thermal radiation

Abstract

The present invention discloses a preparation method of a carbon-based aerogel composite material with strong infrared thermal radiation, comprising the following steps: (1) activating green algae to obtain carbon fibers, and subjecting the carbon fibers to freeze-drying treatment to obtain aerogel fibers having a three-dimensional network structure; (2) immersing the heat-treated aerogel fibers in a mixed solution containing tetrabutyl titanate and hydrochloric acid, and performing a hydrothermal reaction to obtain an aerogel composite material; the aerogel composite material uses carbon fibers as a substrate, and titanium dioxide nanorods are grown on the rod-shaped carbon fiber substrate; wherein, the heat treatment temperature of the aerogel fibers is 700-720 °C; (3) cleaning and drying the composite material obtained in step (2) to obtain the target product.

Description

Technical Field

[0001] The present invention relates to a preparation method of a carbon-based aerogel composite material with strong infrared thermal radiation. Background Art

[0002] With the rapid development of 5G communication technology, people increasingly rely on the application of electronic devices in their lives, and the radiation pollution caused by electromagnetic waves has become an issue that cannot be ignored. Therefore, developing efficient electromagnetic wave absorbers is of great significance for ensuring the normal operation of precision electronic devices and protecting people's health.

[0003] Currently, electromagnetic wave absorbing materials come in various forms, mainly including powders, thin films, aerogels, etc. Different forms of electromagnetic wave absorbing materials lead to different application fields. Among them, as an ultra-light solid material, aerogels have been widely studied by researchers due to their excellent heat insulation performance and extremely low thermal conductivity. The sources of synthetic aerogels are also very diverse, ranging from inorganic compounds (silica, metal oxides) to organic substances (resorcinol, formaldehyde, polyoxymethylene). However, eco-friendly and low-cost composite materials seem to have more development value. Many cellulose-based aerogels are manufactured by extracting cellulose from bagasse, coconut shells, pineapple leaves, and rice straws. Although the sources are extensive, the process of extracting cellulose is also time-consuming and laborious. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide a method for directly preparing a carbon-based aerogel composite material with strong infrared thermal radiation using biomass raw materials.

[0005] Technical Solution: The preparation method of the carbon-based aerogel composite material with strong infrared thermal radiation according to the present invention includes the following steps:

[0006] (1) After activating green algae, carbon fibers (biomass-based carbon fibers) are obtained. The carbon fibers are freeze-dried to obtain aerogel fibers with a three-dimensional network structure.

[0007] (2) The heat-treated aerogel fibers are immersed in a mixed solution containing tetrabutyl titanate and hydrochloric acid for hydrothermal reaction. After the reaction, an aerogel composite material is obtained. The aerogel composite material uses carbon fibers as the substrate, and titanium dioxide nanorods are grown on the rod-shaped carbon fiber substrate. Among them, the heat treatment temperature of the aerogel fibers is 700 - 720 °C. When the heat treatment temperature is lower than 700 °C, the carbon fibers cannot be completely carbonized, resulting in extremely poor conductivity and being unfavorable for the electromagnetic wave absorption performance. When the temperature is higher than 700 °C, the surface structure of the carbon fibers is gradually damaged, which is not conducive to serving as the growth site for the later titanium source.

[0008] (3) The composite material obtained in step (2) is cleaned and dried to obtain the target product.

[0009] Among them, in step (1), the specific process of activating the green algae is as follows: Immerse the green algae in a mixed solution of NaClO - H2SO4, take it out after ultrasonic treatment, and then immerse it in an aqueous solution of ethanol, and take it out to obtain carbon fiber. NaClO and H2SO4 react to produce hypochlorous acid (3H2SO4 + 6NaClO = 3Na2SO4 + 2HCl + 2H2O + 2Cl2 + 2O2; Cl2 + H2O = HCl + HClO), and the formed hypochlorous acid is used to destroy the chlorophyll on the surface of the green algae; then immersing it in the ethanol solution can remove impurities on the one hand and activate the carbon fiber on the other hand.

[0010] Among them, in the NaClO - H2SO4 mixed solution, the concentration of NaClO is 2.7 mol / L, and the concentration of H2SO4 is 0.6 mol / L.

[0011] Among them, in step (2), take a tetrabutyl titanate solution with a concentration of 0.5 mol / L and dissolve it in a hydrochloric acid solution with a concentration of 1 mol / L to obtain a mixed solution containing tetrabutyl titanate and hydrochloric acid, and the pH value of the mixed solution containing tetrabutyl titanate and hydrochloric acid is 3 - 4. The flower - shaped titanium dioxide nanorod arrays formed by hydrothermal reaction grow uniformly on the surface of the rod - shaped carbon fiber. Since there are a large number of titanium - carbon bonds between the carbon fiber substrate and titanium dioxide, titanium dioxide can be stably wrapped on the surface of the carbon fiber substrate; the uniformly and densely wrapped titanium dioxide nanorod array network layer on the surface is beneficial to improving the electromagnetic wave absorption performance and ultraviolet protection performance of the composite material. Hydrochloric acid is used to activate the titanium source, promote hydrolysis, generate titanium tetrachloride (Ti 4+ ) and then hydrolyze it into Ti 2+ .

[0012] Among them, in step (2), the hydrothermal reaction temperature is 135 - 140 °C, and the hydrothermal reaction time is 5.5 - 6 h; the heat treatment time is 1.5 - 2 h. If the heat treatment time is too long or the hydrothermal temperature is too high, the structure of the carbon fiber substrate will be damaged, resulting in an unsatisfactory dielectric constant and ultimately a reduction in the electromagnetic wave absorption performance.

[0013] Among them, in step (2), the titanium dioxide nanorod arrays grown on the carbon fiber substrate are arranged in a flower shape. By performing heat treatment on the aerogel fiber at 700 °C, the wrinkles formed on the carbon fiber substrate are beneficial to the growth of rutile - type titanium dioxide and the formation of a flower - shaped array. The flower - shaped titanium dioxide nanorod arrays can construct a heterostructure on the carbon fiber substrate and enhance the surface area of the carbon fiber, thereby promoting the migration of carriers, improving the conductivity of the composite material, and further enhancing the conductive loss; at the same time, the flower - shaped titanium dioxide nanorod arrays can also enhance the defect - type dipole polarization, improve the polarization loss, enhance the dielectric loss of the formed composite material, promote the attenuation of electromagnetic waves, and further improve the wave - absorbing performance of the material.

[0014] Among them, in step (2), the mass ratio of the carbon fiber substrate to the titanium dioxide nanorod array is 2.1-4.2:1.

[0015] Among them, in step (3), the drying temperature is 30-35°C and the drying time is 10-12 h. An appropriate drying temperature can avoid shape defects caused by excessive shrinkage during the drying of the aerogel fiber, which affects its mechanical properties.

[0016] In the present invention, a flower-shaped rutile-type titanium dioxide network layer is grown on the surface of the rod-shaped carbon fiber substrate obtained after the activation and heat treatment of green algae. The titanium dioxide on the carbon fiber substrate is bonded to the carbon fiber substrate through titanium-carbon bonds. The flower-shaped titanium dioxide nanorod array grows uniformly on the fiber skeleton carbon fiber substrate. The titanium dioxide nanorod array in-situ grown on the carbon fiber skeleton can be stably coated on the surface of the rod-shaped carbon fiber substrate, and the titanium dioxide nanorod array structure with a rutile crystal form has good electrical conductivity, dielectric constant and ultraviolet resistance, thereby enhancing the electromagnetic wave absorption performance, anti-ultraviolet radiation and heat insulation performance of the carbon-based aerogel composite material. The aerogel composite material of the present invention has strong infrared thermal radiation heat insulation performance, electromagnetic wave absorption performance and good ultraviolet resistance at a low thickness.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) The present invention uses green algae fiber to obtain biomass-based carbon fiber, which not only has high preparation efficiency but also can turn waste into treasure; (2) The ultraviolet absorption capacity of the carbon-based aerogel composite material prepared by the present invention can reach more than 95%, and its effective electromagnetic wave absorption bandwidth can reach 7.62 GHz. At a thickness of 2 mm, the minimum value of the reflection loss can reach -41.1 dB; (3) After heating on a heating platform at 150°C for 60 min, the surface of the material always remains at a low temperature (37.5°C); (4) The carbon-based aerogel composite material prepared by the present invention not only meets the electromagnetic wave absorption standards of thin, wide, light and strong, but also has good anti-ultraviolet radiation ability and excellent heat insulation performance caused by infrared thermal radiation. Description of the Drawings

[0018] Figure 1 It is the SEM image of the aerogel fiber prepared in step (1) of Example 1;

[0019] Figure 2 It is the SEM image of the carbon-based aerogel composite material prepared in Example 1;

[0020] Figure 3 It is the X-ray diffraction pattern of the carbon-based aerogel composite material prepared in Example 1;

[0021] Figure 4 It is the XPS analysis pattern of the carbon-based aerogel composite material prepared in Example 1;

[0022] Figure 5 Electromagnetic wave absorption performance diagrams of the carbon-based aerogel composites prepared in Examples 1, 3, 4, and 5;

[0023] Figure 6 Electromagnetic wave absorption performance diagram of the carbon-based aerogel composite prepared in Example 1;

[0024] Figure 7 Ultraviolet absorption capacity diagram of the carbon-based aerogel composite prepared in Example 1;

[0025] Figure 8 Infrared thermal imaging diagram of the carbon-based aerogel composite prepared in Example 1;

[0026] Figure 9 Infrared thermal imaging diagram of the carbon-based aerogel composite prepared in Example 1. Detailed implementation manners

[0027] Example 1

[0028] The preparation method of the carbon-based aerogel composite with strong infrared thermal radiation of the present invention includes the following steps:

[0029] (1) Activation treatment: Immerse 4 g of the initial green algae raw material in the NaClO-H2SO4 mixed solution and stir ultrasonically for 0.5 h; wherein, in the NaClO-H2SO4 mixed solution, the concentration of NaClO is 2.7 mol / L and the concentration of H2SO4 is 0.6 mol / L; after ultrasonic stirring, take it out and immerse it in the aqueous solution of ethanol for 1 h, then take it out to obtain carbon fiber, and put the carbon fiber material into molds with different shapes (the mold shape is cuboid or cylindrical) for freeze-drying treatment to obtain aerogel fibers with a three-dimensional network structure;

[0030] (2) Take a solution of tetrabutyl titanate with a concentration of 0.5 mol / L and dissolve it in a hydrochloric acid solution with a concentration of 1 mol / L for use; Immerse 2.25 g of the aerogel fibers heat-treated at 700 °C for 2 h in the prepared mixed solution containing tetrabutyl titanate and hydrochloric acid, stir evenly and then carry out hydrothermal reaction, and react at 140 °C for 6 h to obtain an aerogel composite;

[0031] (3) Place the aerogel composite in step (2) in an oven at 30 °C and dry it for 12 h to obtain the target product.

[0032] Example 2

[0033] The preparation method of Example 2 is exactly the same as that of Example 1, and the only difference is that the heat treatment temperature in step (2) of Example 2 is 600 °C, and a carbon-based aerogel composite is also obtained after preparation.

[0034] Example 3

[0035] Example 3 has the exact same preparation method as Example 1. The only difference is that the heat treatment temperature in step (2) of Example 3 is 800 °C, and a carbon-based aerogel composite material is also obtained after preparation.

[0036] Example 4

[0037] Example 4 has the exact same preparation method as Example 1. The only difference is that the heat treatment temperature in step (2) of Example 4 is 900 °C, and a carbon-based aerogel composite material is also obtained after preparation.

[0038] Example 5

[0039] Example 5 has the exact same preparation method as Example 1. The only difference is that the heat treatment temperature in step (2) of Example 5 is 1000 °C, and a carbon-based aerogel composite material is also obtained after preparation.

[0040] The carbon-based aerogel composite materials prepared in Examples 1 to 5 were characterized for their microscopic morphology and properties:

[0041] Figure 1 SEM images of the aerogel fibers prepared in step (1) of Example 1 at the 100 μm scale ( Figure 1 a) and 20 μm scale ( Figure 1 b). As can be seen from Figure 1 b, the surface of the carbon fiber is relatively smooth and flat. The aerogel fiber is insulating, has basically no conductivity, and has no wave-absorbing performance.

[0042] Figure 2 SEM images of the carbon-based aerogel composite material prepared in Example 1 at the 20 μm scale ( Figure 2 a) and 1 μm scale ( Figure 2 b). As can be seen from Figure 2 b, when titanium dioxide grows on the surface of the carbon fiber substrate, the surface of the carbon fiber is covered by many flower-like arranged nanoarray substances and becomes rough. These flower-like nanoarrays are the formed rutile-type titanium dioxide nanoarrays.

[0043] Figure 3 X-ray diffraction pattern of the carbon-based aerogel composite material prepared in Example 1. As can be seen from Figure 3 it, the carbon-based aerogel composite material prepared in Example 1 includes the characteristic peaks of carbon fiber and rutile-type titanium dioxide, proving that the synthesized material is a biomass-based carbon fiber - titanium dioxide composite material.

[0044] Figure 4 X-ray photoelectron spectroscopy of the carbon-based aerogel composite material prepared in Example 1. As can be seen from Figure 4 it, the product prepared in Example 1 contains elements such as C, Ti, and O.

[0045] Figure 5 Test diagrams of the electromagnetic wave absorption performance of the carbon-based aerogel composites prepared in Examples 1, 3, 4, and 5. It can be seen from Figure 5 that when the coating thickness is 2 mm, the heat treatment temperature will affect the absorption intensity of the carbon fiber-titanium dioxide aerogel composite. As the heat treatment temperature increases, the minimum reflection loss value decreases (when the heat treatment temperature is 600 °C, the material has no wave absorption performance - the degree of graphitization of the substrate is too low to form a complete conductive network on it, and the conductivity is extremely low). When the heat treatment temperature is 700 °C, the obtained composite material has the best electromagnetic wave absorption performance, and its wave absorption performance has a maximum reflection loss of about -41.1 dB. If the heat treatment temperature is too low, the substrate is incompletely carbonized and the conductivity is extremely poor. If the heat treatment temperature is too high, the carbon fiber substrate will be gradually damaged, which is not conducive to the subsequent growth of rutile titanium dioxide and the formation of a flower-like structure, resulting in a decrease in its electromagnetic wave absorption performance. Therefore, when the heat treatment temperature is 700 °C, the carbon fiber substrate is most suitable for growing flower-like rutile titanium dioxide nanorods, and thus the material has the best wave absorption performance.

[0046] Figure 6 Test diagram of the electromagnetic wave absorption performance of the carbon-based aerogel composite prepared in Example 1. It can be seen from Figure 6 that when the heat treatment temperature is 700 °C and the coating thickness is 2 mm, the reflection loss of the obtained carbon-based aerogel composite reaches the best at -41.1 dB; the effective absorption bandwidth can be as wide as 7.62 GHz at most.

[0047] Figure 7 Absorption performance diagram of ultraviolet rays of the carbon-based aerogel composite prepared in Example 1. It can be seen from Figure 7 that the composite material prepared in Example 1 can absorb more than 95% of ultraviolet rays.

[0048] Figure 8 Infrared thermal imaging diagram of the carbon-based aerogel composite prepared in Example 1. It can be seen from Figure 8 that the composite material prepared in Example 1 has excellent heat insulation performance due to excellent infrared thermal radiation. When the temperature of the heating stage is 150 °C, within 35 minutes of heating, the temperature of the aerogel does not show any obvious rapid increase, and the infrared emissivity of the aerogel is 0.75 at this time.

[0049] Figure 9 Infrared thermal imaging diagram of the carbon-based aerogel composite prepared in Example 1. It can be seen from Figure 9It can be seen that the composite material prepared in Example 1 has excellent heat insulation performance caused by infrared thermal radiation. When the temperature of the heating stage is 150 °C and heated for 360 min, there is no obvious rapid temperature rise of the aerogel, and the surface of the material always remains at a low temperature (37.5 °C). At this time, the infrared emissivity of the aerogel is 0.75. For the aerogel fiber prepared in step (1) of Example 1, when the temperature of the heating stage is 150 °C and heated for 30 seconds, the temperature of the aerogel rises rapidly, and the surface temperature of the material reaches 43.9 °C. The thermal conductivity is related to the direction of heat flow. The flower-shaped nanoarray can improve the direction of heat flow conduction, making the conduction directions different and dispersed, which is beneficial to reducing its thermal conductivity. Combining with the high porosity of the aerogel fiber, the composite material has good heat insulation performance.

Claims

1. A preparation method of a carbon-based aerogel composite material with strong infrared thermal radiation, characterized in that, It includes the following steps: (1) Activate green algae to obtain carbon fiber, and subject the carbon fiber to freeze-drying treatment to obtain aerogel fiber with a three-dimensional network structure; (2) Immerse the heat-treated aerogel fiber in a mixed solution containing tetrabutyl titanate and hydrochloric acid for hydrothermal reaction, and obtain an aerogel composite material after the reaction; the aerogel composite material uses carbon fiber as the substrate, and titanium dioxide nanorods are grown on the rod-shaped carbon fiber substrate; wherein, the heat treatment temperature of the aerogel fiber is 700-720 °C; (3) Wash and dry the composite material in step (2) to obtain the target product; The aerogel composite material prepared by the above method has strong infrared thermal radiation insulation performance, electromagnetic wave absorption performance and good ultraviolet protection ability at low thickness.

2. The preparation method of the carbon-based aerogel composite material with strong infrared thermal radiation according to claim 1, characterized in that: In step (1), the specific process of activating green algae is as follows: Immerse green algae in a NaClO-H2SO4 mixed solution, take it out after ultrasonic treatment, and then immerse it in an ethanol solution for soaking to obtain carbon fiber.

3. The preparation method of the carbon-based aerogel composite material with strong infrared thermal radiation according to claim 2, characterized in that: In the NaClO-H2SO4 mixed solution, the concentration of NaClO is 2.7 mol / L, and the concentration of H2SO4 is 0.6 mol / L.

4. The preparation method of the carbon-based aerogel composite material with strong infrared thermal radiation according to claim 1, characterized in that: In step (2), take a tetrabutyl titanate solution with a concentration of 0.5 mol / L and dissolve it in a hydrochloric acid solution with a concentration of 1 mol / L to obtain a mixed solution containing tetrabutyl titanate and hydrochloric acid.

5. The preparation method of the carbon-based aerogel composite material with strong infrared thermal radiation according to claim 1, characterized in that: In step (2), the hydrothermal reaction temperature is 135-140 °C, and the hydrothermal reaction time is 5.5-6 h; the heat treatment time is 1.5-2 h.

6. The preparation method of the carbon-based aerogel composite material with strong infrared thermal radiation according to claim 1, characterized in that: In step (2), the titanium dioxide nanorods grown on the carbon fiber substrate are arranged in a flower shape.

7. The preparation method of the carbon-based aerogel composite material with strong infrared thermal radiation according to claim 1, characterized in that: In step (2), the mass ratio of the carbon fiber substrate to the titanium dioxide nanorods is 2.1-4.2:

1.

8. The preparation method of the carbon-based aerogel composite material with strong infrared thermal radiation according to claim 1, characterized in that: In step (3), the drying temperature is 30-35 °C, and the drying time is 10-12 h.

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