Carbon fiber-based intelligent temperature control electromagnetic shielding paper and preparation process thereof

Abstract

The invention relates to the fields of composite materials, electromagnetic shielding and specialty paper, in particular to carbon fiber-based intelligent temperature control electromagnetic shielding paper and a preparation process thereof. The carbon fiber-based electromagnetic shielding composite paper is prepared by preferably selecting carbon fibers with excellent electric and heat conduction properties as growth substrate fibers, growing vanadium dioxide particles with thermally induced phase change properties on the surfaces of the carbon fibers by a hydrothermal method, then assisting aramid fibrid as an adhesive and adopting a wet papermaking forming process. The composite paper has intelligent electromagnetic shielding performance responding to temperature stimulation, and dynamic shielding of the electromagnetic shielding performance can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, electromagnetic shielding and special paper, and particularly relates to a carbon fiber-based electromagnetic shielding composite paper with vanadium dioxide particles grown on the surface of carbon fibers and a preparation process thereof. BACKGROUND

[0002] The widespread use of electromagnetic waves has brought serious electromagnetic pollution problems, affecting the normal operation of electronic equipment and posing a potential threat to human health. Although traditional electromagnetic shielding materials can meet the demand for electromagnetic shielding to some extent, their performance is usually static and cannot be dynamically adjusted according to changes in the external environment. In practical applications, the electromagnetic environment is often complex and variable. Therefore, there is an urgent need to develop electromagnetic shielding materials with intelligent response characteristics.

[0003] Vanadium dioxide is a typical thermotropic phase change material, and its unique metal-insulator phase transition behavior (critical temperature of about 68℃) can endow the material with reversible electrical conductivity. During the phase transition, the crystal structure of vanadium dioxide changes from low-temperature insulating monoclinic phase to high-temperature metallic tetragonal phase, and the resistivity can drop by 2~4 orders of magnitude. This feature makes it an ideal functional component for temperature-controlled electromagnetic shielding, which can dynamically adjust the reflection / absorption ratio of electromagnetic waves according to the environmental temperature, thereby realizing temperature-controlled intelligent response shielding. However, in the 5G era, the operating self-heating temperature of electronic components and devices is generally not as high as 68℃, and it is difficult to achieve complete opening of electromagnetic shielding performance relying on the heat generated by normal operation of the equipment.

[0004] At present, there have been a large number of studies using vanadium dioxide as a functional component for reversible switching of electromagnetic shielding performance, and intelligent response electromagnetic shielding materials have been developed, such as patents ZL 202411290282.3, ZL 202310752223.2, ZL 202410979203.3, ZL 202310059178.2, etc. However, the phase transition of vanadium dioxide relies on changes in the external environment temperature, which has the defect of not being able to self-heat, limiting its industrial application.

[0005] Carbon fibers are known for their high electrical conductivity, light weight and excellent mechanical strength. Its three-dimensional conductive network structure can provide an efficient electromagnetic wave reflection path, dissipating the incident electromagnetic energy through free electron oscillation, achieving wide-band electromagnetic shielding. In addition, the high thermal conductivity of carbon fibers can promote the uniform distribution of heat inside the composite, assist the synergistic phase change response of vanadium dioxide particles, and its chemical inertness ensures long-term stability in complex environments. In terms of electrothermal performance, carbon fibers have extremely high thermal conductivity, can quickly transfer heat, and have a low coefficient of thermal expansion, allowing carbon fibers to remain stable in high-temperature environments. In terms of electromagnetic shielding, the three-dimensional conductive network structure of carbon fibers enables it to achieve electromagnetic shielding through reflection and absorption of electromagnetic waves, making it an ideal temperature-controlled electromagnetic shielding skeleton material. However, due to the inertness of the carbon fiber surface, the strength of the paper is low, and the interface is weak, which limits its industrial application. SUMMARY

[0006] In view of the weak interface between carbon fibers and vanadium dioxide, low paper strength and difficulty in achieving temperature control response, the present application provides a carbon fiber-based temperature-controlled intelligent electromagnetic shielding composite paper and its preparation process. The present application is realized by the following technical solutions: 1. A carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper and its preparation process, comprising the following steps: S1, using p-xylene, 95% anhydrous ethanol and deionized water to sequentially ultrasonic wash the chopped carbon fibers, to obtain carbon fiber A; S2, using hydrogen peroxide solution to activate the carbon fiber A, to obtain activated carbon fiber B; S3, placing the activated carbon fiber B and vanadium pentoxide in an oxalic acid solvent system to carry out hydrothermal reaction, to prepare carbon fiber C with monoclinic phase (B) vanadium dioxide grown on the surface, and then through annealing treatment to obtain carbon fiber D with tetragonal rutile phase (M) vanadium dioxide grown on the surface; S4, using a wet papermaking process to papermaking the carbon fiber D with tetragonal rutile phase (M) vanadium dioxide grown on the surface, chopped carbon fibers and meta-aramid fibrids in a certain proportion, and then through cold pressing, vacuum drying and hot pressing treatment to prepare a carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper.

[0007] Preferably, in S1, the length of the chopped carbon fibers is 5 mm, the ultrasonic washing time is 30-60 min, and the ratio of carbon fibers to washing solvent is 1-1.5 g:50-75 mL.

[0008] Preferably, in S2, the concentration of the hydrogen peroxide solution is 25 wt%-30 wt%; during the activation treatment, the temperature is 40-60℃, and the time is 80-100 min; the ratio of carbon fiber A to hydrogen peroxide solution is 1-1.5 g:80-100 mL.

[0009] Preferably, in S3, the ratio of activated carbon fiber B, vanadium pentoxide, oxalic acid solution is 1-1.5:2.9-3.4:50-60 mL; the concentration of oxalic acid solution is 0.5-0.7 mol / L; during the hydrothermal reaction, the time is 30-36 h, and the temperature is 180-190 DEG C.

[0010] Preferably, in S3, during the annealing treatment, the temperature is 500-650 DEG C, the heating rate is 5-10 DEG C / min, and the holding time is 2.5-3 h.

[0011] Preferably, in S4, the average fiber length of the meta-aramid fiber is 0.6-1.0 mm, the fibrillation degree is 45-55 °SR, and the specific surface area is 8-12 m 2 / g; the blending ratio of the carbon fiber, the chopped carbon fiber and the meta-aramid fiber is 40-60 wt%:25-40 wt%:15-30 wt%.

[0012] Preferably, in S4, the parameters of the wet papermaking process are as follows: the dehydration time is 5-10 s, and the vacuum suction pressure is 1-5 MPa.

[0013] Preferably, in S4, during the cold pressing treatment, the temperature is 20-40 DEG C, the pressure is 5-10 MPa, and the time is 5-8 min; During the hot pressing treatment, the pressure is 10-15 MPa, the temperature is 130-180 DEG C, and the time is 15-20 min.

[0014] Preferably, in S4, during the vacuum drying treatment, the temperature is 100-105 DEG C, the vacuum degree is 0.6-0.9 MPa, and the drying time is 10-15 min.

[0015] A carbon fiber-based intelligent temperature control electromagnetic shielding paper prepared by the preparation process of the carbon fiber-based intelligent temperature control electromagnetic shielding paper.

[0016] Compared with the prior art, the present application has the following beneficial effects: The present application discloses a preparation process of a carbon fiber-based temperature control intelligent electromagnetic shielding composite paper.

[0017] Further, in view of the weak interface bonding between carbon fibers and vanadium dioxide, low paper strength and poor temperature control response stability, the application introduces carbon fibers as conductive shielding skeleton material. On the one hand, the carbon fibers can build a continuous conductive path by virtue of their high conductivity and three-dimensional network structure, reflect electromagnetic waves through free electron oscillation, and provide basic electromagnetic shielding effectiveness. On the other hand, since the carbon fibers have high specific surface area and excellent mechanical strength, they can provide sufficient anchoring sites for vanadium dioxide loading while maintaining the structural stability of the composite paper.

[0018] Further, in view of the weak interface bonding between carbon fibers and vanadium dioxide, low paper strength and poor temperature control response stability, the application introduces carbon fibers as conductive shielding skeleton material. On the one hand, the carbon fibers can build a continuous conductive path by virtue of their high conductivity and three-dimensional network structure, reflect electromagnetic waves through free electron oscillation, and provide basic electromagnetic shielding effectiveness. On the other hand, since the carbon fibers have high specific surface area and excellent mechanical strength, they can provide sufficient anchoring sites for vanadium dioxide loading while maintaining the structural stability of the composite paper.

[0019] Further, the meta-aramid fibrid is introduced as an auxiliary forming fiber, filler and adhesive, which can effectively fill the pores between carbon fibers and significantly improve the interlayer bonding force of the composite paper through hydrogen bonding and mechanical interlocking. The intrinsic flame-retardant property and high temperature resistance of the meta-aramid fibrid make up for the flammable defect of the carbon fiber, and the low dielectric constant ensures that the electromagnetic shielding effectiveness of the carbon fiber will not be disturbed. The flexible form of the fibrid is more conducive to the wet forming process, realizing uniform dispersion of the functional components.

[0020] Further, the application introduces oxygen-containing groups on the surface of the carbon fibers through acid treatment, improves the hydrophilicity and reactivity of the carbon fibers, anchors the vanadium dioxide crystal nucleus through hydrogen bonding, reduces the pentavalent vanadium to tetravalent vanadium during the hydrothermal reaction process, and uniformly and stably loads the tetravalent vanadium on the surface of the carbon fibers through chemical bonding, significantly improving the interface bonding strength and avoiding the problem of easy peeling of the VO2 particles on the surface of the paper in the traditional physical mixing method, while ensuring the sensitivity and reliability of the temperature control response.

[0021] Further, the application adopts high-temperature hot pressing process to strengthen the connection of the carbon fiber network, promote the softening and bonding of the meta-aramid fibrid, fill the pores between the carbon fibers, improve the paper density, and enhance the continuity of the conductive path.

[0022] Further, the carbon fibers and meta-aramid fibrid used in the application are industrialized mass production raw materials, and the forming process (wet forming + hot pressing) is compatible with existing papermaking equipment, providing a feasible path for the large-scale production of temperature control intelligent electromagnetic shielding materials. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A flow chart of a preparation process of a carbon fiber-based temperature-controlled intelligent electromagnetic shielding composite paper according to the present application is shown in FIG. 1. Figure 2 A SEM image of carbon fiber D on which tetragonal rutile phase (M) vanadium dioxide is grown on the surface prepared in S3 of the present application is shown in FIG. 2. Figure 3 A surface SEM image of the composite paper prepared in Example 1 is shown in FIG. 3. Figure 4 A trend graph of the electromagnetic shielding performance of the composite paper prepared in Example 1 at different frequencies and different temperatures is shown in FIG. 4. Figure 5 A thermoelectric response curve of the composite paper prepared in Example 1 at different voltages is shown in FIG. 5. Figure 6 XRD images of the composite papers prepared in Examples 1-3 are shown in FIG. 6. Figure 7 Tensile strength characterization graphs of the composite papers prepared in Examples 1-3 are shown in FIG. 7. Figure 8 Electromagnetic shielding efficiency characterization graphs of the composite papers prepared in Examples 1-3 at different temperatures are shown in FIG. 8. DETAILED DESCRIPTION

[0024] The present application will be further described in detail below with reference to specific examples, which are intended to explain but not limit the present application.

[0025] The present application discloses a preparation process of a carbon fiber-based temperature-controlled intelligent electromagnetic shielding composite paper, referring to FIG. 1. Figure 1 , comprising the following steps: S1, using p-xylene, 95% anhydrous ethanol and deionized water to sequentially ultrasonically wash short-cut carbon fibers to obtain carbon fibers A; wherein the length of the short-cut carbon fibers is 5 mm, the ultrasonic washing time is 30-60 min, and the ratio of the carbon fibers to the washing solvent is 1-1.5 g:50-75 mL.

[0026] S2, using a hydrogen peroxide solution with a concentration of 25 wt%-30 wt% to activate-process the carbon fibers A to obtain activated carbon fibers B; wherein the ratio of the carbon fibers to the hydrogen peroxide solution is 1-1.5 g:80-100 mL; during the activation processing, the temperature is 40-60 ℃, and the time is 80-100 min.

[0027] S3, placing the activated carbon fibers B and vanadium pentoxide in an oxalic acid solvent system with a concentration of 0.5-0.7 mol / L to perform a hydrothermal reaction to prepare carbon fibers C on which monoclinic phase (B) vanadium dioxide is grown on the surface, and then performing an annealing treatment to obtain carbon fibers D on which tetragonal rutile phase (M) vanadium dioxide is grown on the surface.

[0028] The ratio of the carbon fiber B, the vanadium pentoxide and the oxalic acid solution is 1-1.5:2.9-3.4:50-60 mL. During the hydrothermal reaction, the time is 30-36 h, and the reaction temperature is 180-190 DEG C. During the annealing treatment, the temperature is 500-650 DEG C, the heating rate is 5-10 DEG C / min, and the holding time is 2.5-3 h.

[0029] S4, the carbon fiber D with the surface growth of the tetragonal rutile phase (M) vanadium dioxide, the chopped carbon fiber and the meta-aramid fibrid are papered according to a certain proportion by using a wet papermaking process, and then the carbon fiber-based intelligent temperature control electromagnetic shielding paper is prepared through cold pressing, vacuum drying and hot pressing treatment.

[0030] The average fiber length of the meta-aramid fibrid is 0.6-1.0 mm, the fibrillation degree is 45-55 °SR, the specific surface area is 8-12 m 2 / g, The papermaking proportion of the carbon fiber with the surface growth of vanadium dioxide particles, the chopped carbon fiber and the meta-aramid fibrid is 40-70 wt%:20-40 wt%:10-30 wt%.

[0031] The parameters of the wet forming process are as follows: the dehydration time is 5-10 s, and the vacuum suction pressure is 1-5 MPa. During the cold pressing treatment, the temperature is 20-40 DEG C, the pressure is 5-10 MPa, and the pressing time is 5-8 min. During the vacuum drying treatment, the temperature is 100-105 DEG C, the vacuum degree is 0.6-0.9 MPa, and the drying time is 10-15 min. During the hot pressing treatment, the pressure is 10-15 MPa, the temperature is 130-180 DEG C, and the time is 15-20 min.

[0032] The carbon fiber-based temperature control intelligent electromagnetic shielding composite paper preparation process of the application takes the carbon fiber as the conductive framework material, and realizes the temperature control intelligent response function by using the in-situ growth technology of vanadium dioxide, solves the problems of static shielding, application scene limitation and the like of the traditional shielding material. Meanwhile, by introducing the meta-aramid fibrid as the adhesive and the meta-aramid short fiber as the reinforcing fiber, the interface bonding strength and the temperature response stability of the composite paper are effectively improved. By using the wet forming + hot pressing technology, the raw materials are easy to obtain, the energy consumption is low, and the technology is compatible with the existing papermaking equipment, so that a reliable solution scheme is provided for the industrial application of the intelligent electromagnetic shielding material, and the economic benefit and market competitiveness are remarkable.

[0033] Example 1 S1, weigh 1g of short-cut carbon fiber, pour in 50mL of p-xylene, and perform ultrasonic washing for 30min. Then, perform the same ultrasonic washing operation with anhydrous ethanol and deionized water in sequence. After washing, remove the moisture by vacuum filtration and place it in a vacuum drying oven at 105℃ for 12h to obtain washed carbon fiber A. S2, the above carbon fiber A is placed in a 30wt% hydrogen peroxide solution, stirred in a water bath at 45°C for 80 min, the hydrogen peroxide solution is removed by vacuum filtration, then washed 3 times with deionized water, and dried in a vacuum drying oven at 105°C for 12 h to obtain activated carbon fiber B. S3, the activated carbon fiber B was placed in 60 mL of 0.5 mol / L oxalic acid solution, and 2.91 g of vanadium pentoxide was added. After stirring for 30 min, the mixture was transferred to a 100 mL hydrothermal reactor. The hydrothermal reaction time was 36 h, and the reaction temperature was 190 °C, to obtain carbon fiber C with surface-grown monoclinic phase (B) vanadium dioxide. Then, carbon fiber C was placed in a tube furnace for annealing at 550 °C, with a heating rate of 5 °C / min and a holding time of 2.5 h, to obtain carbon fiber D with surface-grown tetragonal rutile phase (M) vanadium dioxide. S4. A wet papermaking process was used to form carbon fiber D with surface-grown tetragonal rutile (M) vanadium dioxide, along with carbon fiber and meta-aramid precipitated fiber in a ratio of 70wt%:20wt%:10wt%. After hot pressing, carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper was obtained. The parameters for the wet forming process were: dehydration time 10s, vacuum suction pressure 3.5MPa; cold pressing temperature 26℃, pressure 5MPa, pressing time 8min; vacuum drying temperature 105℃, vacuum degree 0.6MPa, drying time 10min; hot pressing pressure 10MPa, temperature 155℃, time 15min.

[0034] Reference Figures 3-8 The carbon fiber-based temperature-controlled intelligent electromagnetic shielding composite paper obtained in Example 1 achieved a temperature response in electromagnetic shielding performance. It has a thickness of 0.154 mm, a tensile strength of 2.72 MPa, and can be heated to 140°C by applying a 14V DC voltage. Figure 2 As can be seen, vanadium dioxide is tightly loaded on the surface of carbon fibers, with a basic morphology of hexagonal starfruit shape. (From...) Figure 3 It is evident that the carbon fibers intertwine with the vanadium dioxide-loaded carbon fibers to construct a three-dimensional conductive and thermally conductive network. The aramid precipitated fibers act as a binder, enhancing the interlayer bonding between fibers and ensuring the paper strength to a certain extent. The electromagnetic shielding performance ranges from a minimum of 23dB to a maximum of 34dB in the 8.2–12.4 GHz frequency band, achieving temperature-controlled intelligent electromagnetic shielding.

[0035] Example 2 S1, weigh 1.5g of short-cut carbon fiber, pour in 75mL of p-xylene, and perform ultrasonic washing for 40min. Then, perform the same ultrasonic washing operation with anhydrous ethanol and deionized water in sequence. After washing, remove the moisture by vacuum filtration and dry in a vacuum drying oven at 105℃ for 12h to obtain carbon fiber A. S2, the above carbon fiber A is placed in a 25wt% hydrogen peroxide solution, stirred in a water bath at 50°C for 90 min, the hydrogen peroxide solution is removed by vacuum filtration, then washed 3 times with deionized water, and dried in a vacuum drying oven at 105°C for 12 h to obtain activated carbon fiber B. S3, the activated carbon fibers were placed in 60 mL of 0.5 mol / L oxalic acid solution, 2.91 g of vanadium pentoxide was added, and after stirring for 30 min, the mixture was transferred to a 100 mL hydrothermal reactor. The hydrothermal reaction time was 36 h and the reaction temperature was 190 °C to obtain carbon fiber C with surface-grown monoclinic phase (B) vanadium dioxide. Carbon fiber C was placed in a tube furnace for annealing treatment at a temperature of 500 °C, a heating rate of 5 °C / min, and a holding time of 2.7 h to obtain carbon fiber D with surface-grown tetragonal rutile phase (M) vanadium dioxide. S4. Using a wet papermaking process, the carbon fiber D described in S3, along with carbon fiber and meta-aramid precipitated fiber, are formed into paper in a ratio of 66wt%:24wt%:10wt%. After hot pressing, carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper is obtained. The parameters for the wet forming process are as follows: dehydration time is 10s, vacuum suction pressure is 3MPa; during cold pressing, the temperature is 24℃, the pressure is 5MPa, and the pressing time is 8min; during vacuum drying, the temperature is 100℃, the vacuum degree is 0.7MPa, and the drying time is 10min; during hot pressing, the pressure is 10MPa, the temperature is 160℃, and the time is 15min.

[0036] The carbon fiber-based temperature-controlled intelligent electromagnetic shielding composite paper obtained in Example 2 achieved a temperature response in electromagnetic shielding performance. It has a thickness of 0.175 mm, a tensile strength of 2.19 MPa, and can be heated to 130°C by applying a 14V DC voltage. (Refer to...) Figure 8 The electromagnetic shielding performance ranges from a minimum of 22dB to a maximum of 29dB in the 8.2–12.4 GHz frequency band, achieving temperature-controlled intelligent electromagnetic shielding.

[0037] Example 3 S1, weigh 1g of short-cut carbon fiber, pour in 50mL of p-xylene, and perform ultrasonic washing for 50min. Then, perform the same ultrasonic washing operation with anhydrous ethanol and deionized water in sequence. After washing, remove the moisture by vacuum filtration and place it in a vacuum drying oven at 105℃ for 12h to obtain carbon fiber A. S2, the above carbon fiber A was placed in a 27wt% hydrogen peroxide solution, stirred in a water bath at 50°C for 95 min, the hydrogen peroxide solution was removed by vacuum filtration, and then washed three times with deionized water. It was then placed in a vacuum drying oven and dried at 105°C for 12 h to obtain activated carbon fiber B. S3, the activated carbon fibers were placed in 60 mL of 0.5 mol / L oxalic acid solution, 2.91 g of vanadium pentoxide was added, and after stirring for 30 min, the mixture was transferred to a 100 mL hydrothermal reactor. The hydrothermal reaction time was 36 h and the reaction temperature was 190 °C to obtain carbon fiber C with surface-grown monoclinic phase (B) vanadium dioxide. Carbon fiber C was placed in a tube furnace for annealing treatment at a temperature of 600 °C, a heating rate of 10 °C / min, and a holding time of 3 h to obtain carbon fiber D with surface-grown tetragonal rutile phase (M) vanadium dioxide. S4. Using a wet papermaking process, carbon fiber D described in S3, along with carbon fiber and meta-aramid precipitated fiber, are formed into paper in a ratio of 60wt%:30wt%:10wt%. After hot pressing, carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper is obtained. The parameters for the wet forming process are as follows: dehydration time is 10s, vacuum suction pressure is 4MPa; during cold pressing, the temperature is 26℃, the pressure is 5MPa, and the pressing time is 8min; during vacuum drying, the temperature is 100℃, the vacuum degree is 0.8MPa, and the drying time is 15min; during hot pressing, the pressure is 12MPa, the temperature is 150℃, and the time is 10min.

[0038] The carbon fiber-based temperature-controlled intelligent electromagnetic shielding composite paper obtained in Example 3 achieves temperature response in electromagnetic shielding performance, with a thickness of 0.172 mm and a tensile strength of 1.75 MPa. By applying a 14V DC voltage to it, the composite paper can be heated to 80°C.

[0039] Example 4 S1, weigh 1g of short-cut carbon fiber, pour in 60mL of p-xylene, and perform ultrasonic washing for 35min. Then, perform the same ultrasonic washing operation with anhydrous ethanol and deionized water in sequence. After washing, remove the moisture by vacuum filtration and place it in a vacuum drying oven at 105℃ for 12h to obtain washed carbon fiber A. S2, the above carbon fiber A was placed in a 26wt% hydrogen peroxide solution, stirred in a water bath at 45°C for 82 min, the hydrogen peroxide solution was removed by vacuum filtration, and then washed three times with deionized water. It was then placed in a vacuum drying oven and dried at 105°C for 12 h to obtain activated carbon fiber B. S3, the activated carbon fiber B was placed in 60 mL of 0.5 mol / L oxalic acid solution, and 2.95 g of vanadium pentoxide was added. After stirring for 30 min, the mixture was transferred to a 100 mL hydrothermal reactor. The hydrothermal reaction time was 32 h, and the reaction temperature was 185 °C, to obtain carbon fiber C with surface-grown monoclinic phase (B) vanadium dioxide. Then, carbon fiber C was placed in a tube furnace for annealing at a temperature of 560 °C, a heating rate of 6 °C / min, and a holding time of 2.6 h, to obtain carbon fiber D with surface-grown tetragonal rutile phase (M) vanadium dioxide. S4. A wet papermaking process was used to form carbon fiber D with surface-grown tetragonal rutile (M) vanadium dioxide, along with carbon fiber and meta-aramid precipitated fiber, in a ratio of 68wt%:22wt%:10wt%. After hot pressing, carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper was obtained. The parameters for the wet forming process were: dehydration time 10s, vacuum suction pressure 4MPa; cold pressing temperature 26℃, pressure 5MPa, pressing time 8min; vacuum drying temperature 105℃, vacuum degree 0.6MPa, drying time 10min; hot pressing pressure 10MPa, temperature 145℃, time 13min.

[0040] The carbon fiber-based temperature-controlled intelligent electromagnetic shielding composite paper obtained in Example 4 achieves temperature response in electromagnetic shielding performance, with a thickness of 0.175 mm and a tensile strength of 2.65 MPa. By applying a 14V DC voltage to it, the composite paper can be heated to 135°C.

[0041] Example 5 S1, weigh 1g of short-cut carbon fiber, pour in 65mL of p-xylene, and perform ultrasonic washing for 45min. Then, perform the same ultrasonic washing operation with anhydrous ethanol and deionized water in sequence. After washing, remove the moisture by vacuum filtration and place it in a vacuum drying oven at 105℃ for 12h to obtain washed carbon fiber A. S2, the above carbon fiber A was placed in a 28wt% hydrogen peroxide solution, stirred in a water bath at 45°C for 92 min, the hydrogen peroxide solution was removed by vacuum filtration, and then washed three times with deionized water. It was then placed in a vacuum drying oven and dried at 105°C for 12 h to obtain activated carbon fiber B. S3, the activated carbon fiber B was placed in 60 mL of 0.5 mol / L oxalic acid solution, 3.0 g of vanadium pentoxide was added, and after stirring for 30 min, it was transferred to a 100 mL hydrothermal reactor. The hydrothermal reaction time was 34 h, and the reaction temperature was 187 °C, to obtain carbon fiber C with surface-grown monoclinic phase (B) vanadium dioxide. Then, carbon fiber C was placed in a tube furnace for annealing treatment at a temperature of 570 °C, a heating rate of 7 °C / min, and a holding time of 2.7 h, to obtain carbon fiber D with surface-grown tetragonal rutile phase (M) vanadium dioxide. S4. A wet papermaking process was used to produce carbon fiber D with surface-grown tetragonal rutile (M) vanadium dioxide, along with carbon fiber and meta-aramid precipitated fiber in a ratio of 63wt%:27wt%:10wt%. After hot pressing, carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper was obtained. The parameters for the wet forming process were: dehydration time 10s, vacuum suction pressure 4MPa; cold pressing temperature 26℃, pressure 5MPa, pressing time 8min; vacuum drying temperature 105℃, vacuum degree 0.6MPa, drying time 10min; hot pressing pressure 10MPa, temperature 165℃, time 15min.

[0042] The carbon fiber-based temperature-controlled intelligent electromagnetic shielding composite paper obtained in Example 5 achieved a temperature response in electromagnetic shielding performance. It has a thickness of 0.173 mm and a tensile strength of 2.03 MPa. By applying a 14 V DC voltage to it, the composite paper can be heated to 120 °C.

[0043] Depend on Figure 6 It can be seen that the characteristic diffraction peaks of pitch-based carbon fibers are at 2θ of 26.5° and 54.5°, corresponding to the (002) and (10) crystal planes, respectively. Furthermore, 27.8°, 37.0°, 42.2°, 55.4°, 57.4°, 65.0°, and 70.3° correspond to the characteristic peaks of the seven crystal planes of VO2(M). (Refer to...) Figure 8 The electromagnetic shielding performance ranges from a minimum of 20dB to a maximum of 34dB in the 8.2–12.4 GHz frequency band, achieving temperature-controlled intelligent electromagnetic shielding.

[0044] This invention discloses a process for preparing carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper. The process utilizes carbon fibers with excellent conductivity as the growth substrate fiber. Vanadium dioxide particles with thermo-induced phase change properties are hydrothermally grown on the surface of the carbon fiber substrate, and aramid precipitated fibers are used as a binder. A wet papermaking process is then employed to prepare a carbon fiber-based electromagnetic shielding composite paper. This composite paper possesses intelligent electromagnetic shielding performance that responds to temperature stimuli, enabling dynamic response of electromagnetic shielding performance.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper and its preparation process, characterized in that, Includes the following steps: S1, short-cut carbon fibers were ultrasonically washed sequentially with p-xylene, 95% anhydrous ethanol and deionized water to obtain carbon fiber A; S2, carbon fiber A is activated using hydrogen peroxide solution to obtain activated carbon fiber B; S3, activated carbon fiber B and vanadium pentoxide are placed in an oxalic acid solvent system for hydrothermal reaction to obtain carbon fiber C with monoclinic phase (B) vanadium dioxide grown on the surface, and then carbon fiber D with tetragonal rutile phase (M) vanadium dioxide grown on the surface is obtained by annealing treatment. S4 uses a wet papermaking process to make carbon fiber D with tetragonal rutile phase (M) vanadium dioxide grown on the surface, short-cut carbon fiber, and meta-aramid precipitated fiber in a certain proportion. After cold pressing, vacuum drying and hot pressing, carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper is obtained.

2. The preparation process of carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper according to claim 1, characterized in that, In S1, the length of the short-cut carbon fiber is 5 mm, the ultrasonic washing time is 30~60 min, and the ratio of carbon fiber to washing solvent is 1~1.5 g: 50~75 mL.

3. The preparation process of carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper according to claim 1, characterized in that, In S2, the concentration of hydrogen peroxide solution is 25 wt%~30 wt%; during activation treatment, the temperature is 40~60 ℃ and the time is 80~100 min; the ratio of carbon fiber A to hydrogen peroxide solution is 1~1.5 g: 80~100 mL.

4. The preparation process of carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper according to claim 1, characterized in that, In S3, the ratio of activated carbon fiber B, vanadium pentoxide, and oxalic acid solution is 1~1.5:2.9~3.4:50~60 mL; the concentration of oxalic acid solution is 0.5~0.7 mol / L; the hydrothermal reaction time is 30~36 h and the temperature is 180~190 ℃.

5. The preparation process of carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper according to claim 1, characterized in that, In S3, during annealing, the temperature is 500~650℃, the heating rate is 5~10℃ / min, and the holding time is 2.5~3h.

6. The preparation process of carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper according to claim 1, characterized in that, In S4, the average fiber length of the meta-aramid precipitated fibers is 0.6–1.0 mm, the degree of fibrillation is 45–55°SR, and the specific surface area is 8–12 m². 2 / g; The ratio of carbon fiber, chopped carbon fiber and meta-aramid precipitated fiber with vanadium dioxide particles grown on the surface is 40~70wt%:25~40wt%:15~30wt%.

7. The preparation process of carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper according to claim 1, characterized in that, In S4, the parameters for the wet papermaking process are: dewatering time of 5~10s and vacuum suction pressure of 1~5MPa.

8. The preparation process of carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper according to claim 1, characterized in that, In S4, during cold pressing, the temperature is 20~40℃, the pressure is 5~10MPa, and the time is 5~8min; During hot pressing, the pressure is 10~15MPa, the temperature is 130~180℃, and the time is 15~20min.

9. The preparation process of carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper according to claim 1, characterized in that, In S4, during vacuum drying, the temperature is 100~105℃, the vacuum degree is 0.6~0.9MPa, and the drying time is 10~15min.

10. A carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper prepared by the carbon fiber-based intelligent temperature-controlled electromagnetic shielding paper preparation process according to any one of claims 1 to 10.

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