Preparation method of conductive and magnetizable carbonized wood-based electromagnetic shielding material

Abstract

The application discloses a preparation method of a carbonized wood-based electromagnetic shielding material with electrically-conductive and magnetically-conductive properties, which comprises the following steps: immersing Fe3O4@Graphene nanoparticles into the surface of wood after carbonization, and then performing chemical nickel plating to prepare the carbonized wood-based electromagnetic shielding material. The carbonized wood has good corrosion and insect prevention performance, is not easy to absorb water, and is a good moisture-proof wood with a contact angle of 126.2 degrees. Therefore, after the Fe3O4@Graphene nanoparticles are compounded on the surface of the carbonized wood, the chemical nickel plating can endow the carbonized wood with electromagnetic functional properties. By controlling the time for immersing the nanoparticles, the electromagnetic shielding performance of the carbonized wood composite material can be regulated. The conductivity of the carbonized wood composite material prepared after immersing the nanoparticles for 5 hours can reach 631.3 S / cm, and the average electromagnetic shielding efficiency of the carbonized wood composite material in a frequency range of 8.2 to 12.4 GHz can reach 70 dB, and some frequency bands can reach 80 dB.

Description

Technical Field

[0001] This invention relates to the field of material preparation, and more specifically to a method for preparing a carbonized wood-based electromagnetic shielding material with electrical and magnetic conductivity. Background Technology

[0002] Over the past few decades, information technology has developed rapidly, especially communication technologies represented by emerging 5G wireless systems, which have achieved unprecedented success in recent years. However, electromagnetic radiation and interference generated between various electronic devices can seriously affect the normal operation of electronic devices and components, as well as harm human health and pollute the natural environment. In the military field, electromagnetic wave leakage can seriously endanger national defense information security and the protection of state secrets. Electromagnetic shielding materials can effectively protect electronic devices and their environment, prevent electromagnetic information leakage, cut off the propagation path of electromagnetic waves, and suppress electromagnetic radiation and interference, making them one of the important technical means to solve the problem of electromagnetic pollution. Therefore, in order to extend the service life of equipment, improve the electromagnetic compatibility and safety of biological systems, and reduce the impact of electromagnetic radiation on the human body or interfered equipment, electromagnetic shielding materials have emerged and are widely used.

[0003] Wood is mainly composed of cellulose, hemicellulose, and lignin. After carbonization, the internal moisture and composition of wood are carbonized, resulting in a significant reduction in weight and making it lightweight. Furthermore, carbonized wood exhibits good anti-corrosion and insect-repellent properties and is less prone to water absorption, making it an excellent moisture-proof material. Therefore, chemically plating Fe3O4@Graphene nanoparticles onto the surface of carbonized wood followed by electroless nickel plating, and then endowing the carbonized wood with electromagnetic functional properties, is a method for preparing anti-corrosion, moisture-proof, and lightweight electromagnetic shielding materials.

[0004] Currently, there is little research on electromagnetic shielding in carbonized wood. There is a lack of studies on the preparation of electromagnetic shielding materials by chemically plating Ni onto the surface of carbonized wood and using composite Fe3O4@Graphene nanoparticles. This study is the first to prepare an electromagnetic shielding material by chemically plating Ni onto the surface of carbonized wood and using composite Fe3O4@Graphene nanoparticles, and its electromagnetic shielding performance was investigated. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a wood-based electromagnetic shielding material with relatively stable electromagnetic shielding performance at high frequencies. In the frequency range of 8.2 to 12.4 GHz, the electromagnetic shielding performance of the composite material can reach 70 dB, and in some frequency bands it can reach 80 dB.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a carbonized wood-based electromagnetic shielding material with electrical and magnetic conductivity is characterized by carbonizing wood at high temperature, then impregnating its surface with composite Fe3O4@Graphene nanoparticles, and finally preparing it by chemical nickel plating.

[0008] Furthermore, the preparation method of the above-mentioned conductive and magnetic carbonized wood-based electromagnetic shielding material specifically includes the following steps:

[0009] S1. Cut and process the scarless virgin wood into wood blocks, and then put them into a tube furnace for carbonization. After carbonization, screen out flat and crack-free carbonized wood blocks for later use.

[0010] S2. Place FeCl2·4H2O, FeCl3·6H2O and water in container A and stir until completely dissolved. Then place monolayer graphene and anhydrous ethanol in container B and stir evenly. Pour the solution from container A into container B and mix evenly. After stirring magnetically for a period of time, adjust the pH of the solution to 10 to obtain Fe3O4@Graphene nanoparticles. Collect the Fe3O4@Graphene nanoparticles with a magnet, wash and dry them for later use.

[0011] S3. Fe3O4@Graphene nanoparticles and water were placed in a container and magnetically stirred. During the stirring process, carbonized wood blocks from S1 were added and stirred to impregnate the mixture. After impregnation for a period of time, the sample was taken out.

[0012] S4. The sample obtained in S3 is subjected to chemical nickel plating (for the specific method of chemical nickel plating, please refer to patent ZL202110540310.2) to obtain the conductive and magnetic carbonized wood-based electromagnetic shielding material.

[0013] Preferably, in S1, the specifications of the wooden block are: 5-7cm in length, 2.5-3cm in width, and 0.4-0.5cm in thickness.

[0014] Preferably, in S1, the carbonization process includes: turning on the tube furnace, powering on the vacuum pump, setting the program for the tube furnace, placing the wood block into the tube furnace, connecting the tube furnace, filling with nitrogen, slowly increasing the pressure valve from 0 MPa to 0.05 MPa, releasing the pressure and slowly reducing it to 0 MPa, starting the tube furnace after the air inside the tube furnace is exhausted, and the tube furnace will carbonize the sample according to the set program. When "STOP" is displayed on the screen, it indicates that the carbonization is over. First, turn off the nitrogen, and then turn off the instrument after the nitrogen inside the furnace is exhausted. The carbonization process is over.

[0015] The parameters of the tube furnace are as follows: initial temperature: 25℃, heating time: 140min, holding temperature: 700℃, holding time: 120min, initial cooling temperature: 700℃, cooling time: 140min, and final sampling temperature: 25℃.

[0016] Preferably, in S2, the amount of FeCl2·4H2O added is 0.07g, the amount of FeCl3·6H2O added is 0.20g, the amount of water added is 20mL, the amount of monolayer graphene added is 0.20g, and the amount of anhydrous ethanol added is 20mL.

[0017] Preferably, in S2, the magnetic stirring time is 30-60 min and the stirring rate is 100-300 rpm; the pH of the solution is adjusted by using ammonia.

[0018] Preferably, in step S3, the amount of Fe3O4@Graphene nanoparticles added is 0.1-0.5g, and the amount of water added is 100-500mL.

[0019] Preferably, in S3, the soaking time is 1h, 2h, 3h, 4h or 5h.

[0020] Preferably, in S4, the electroless nickel plating process is as follows:

[0021] The method for electroless nickel plating is as follows:

[0022] (1) Preparation of activation solution A: Add 400mL of distilled water to a beaker; add 4.8mL of concentrated hydrochloric acid to the beaker, stir with a glass rod, then add 6g of nickel sulfate granules, pour into the beaker, and stir with a glass rod until completely dissolved.

[0023] (2) Preparation of activation solution B: Add 400mL of distilled water to a beaker; weigh 4.8g of sodium hydroxide and stir until dissolved; then add 6g of sodium borohydride and stir with a glass rod until completely dissolved.

[0024] (3) Preparation of electroless nickel plating solution: Add 600mL of distilled water to a beaker; weigh 19.8g of nickel sulfate and add it, stirring to dissolve; weigh 18g of sodium citrate and add it, stirring to dissolve; weigh 16.8g of sodium hypophosphite and add it, stirring to dissolve; weigh 20mg of thiourea and add it, stirring until dissolved; add ammonia to adjust the pH of the solution to 9-9.5.

[0025] (4) Place the sample in activation solution A for 15 min, flip the sample once every 5 min, take it out, and when there is no liquid dripping from the sample, place it in activation solution B for 90 s seconds, flip the sample once every 30 s, take it out, and place it until there is no liquid dripping from the surface; then place the sample in chemical nickel plating solution at 60℃ for chemical nickel plating treatment, and flip the sample once every 3 min during the nickel plating period.

[0026] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. In the frequency range of 8.2 to 12.4 GHz, the electromagnetic shielding effectiveness of this composite material can be adjusted according to the impregnation time of Fe3O4@Graphene nanoparticles. Depending on the specific impregnation time, a composite material with a shielding effectiveness in the range of 30-70 dB can be prepared.

[0028] 2. The composite material prepared by chemically plating Fe3O4@Graphene nanoparticles onto the surface of carbonized wood not only has excellent electrical conductivity but also good magnetic properties, i.e., electromagnetic compatibility. The electrical conductivity of the composite material prepared under optimal conditions can reach 631.3 S / cm.

[0029] 3. After carbonization, the internal moisture and composition of the wood are carbonized, resulting in a significant reduction in weight and making it lightweight. Furthermore, carbonized wood exhibits good anti-corrosion and insect-repellent properties, and it does not easily absorb water, making it an excellent moisture-proof material. Its contact angle can reach 126.2°, and it possesses electrical conductivity and electromagnetic shielding effectiveness, with electrical conductivity of 0.1 S / cm and electromagnetic shielding effectiveness of 30 dB. Therefore, impregnating the surface of carbonized wood with Fe3O4@Graphene nanoparticles followed by electroless nickel plating can endow the carbonized wood with electromagnetic properties, while simultaneously providing it with anti-corrosion, moisture-proof, lightweight, and electromagnetic shielding material characteristics. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0031] Figure 1 This is a flowchart of a method for preparing a conductive and magnetically permeable carbonized wood-based electromagnetic shielding material according to Embodiment 1 of the present invention;

[0032] Figure 2 The electromagnetic shielding curve of the wood-based electromagnetic shielding material obtained in the embodiments of the present invention is shown.

[0033] Figure 3This is a magnetic illustration of the wood-based electromagnetic shielding material prepared according to the present invention.

[0034] Figure 4 This is a diagram showing the electromagnetic shielding effectiveness of the wood-based electromagnetic shielding material obtained in an embodiment of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides a method for preparing a carbonized wood-based electromagnetic shielding material with electrical and magnetic conductivity, including the following steps:

[0038] S1. Use a cutting machine to process the knot-free native poplar wood (any knot-free wood can be used, poplar wood is used as an example in this embodiment) into poplar wood blocks with a length of 5-7cm, a width of 2.5-3cm, and a thickness of 0.4-0.5cm. Take seven poplar wood blocks of this size and put them into a tube furnace for carbonization treatment. After carbonization, screen out the flat and crack-free carbonized wood blocks for later use.

[0039] The specific carbonization operation steps are as follows: Turn on the tube furnace, power on the vacuum pump, and set the program for the tube furnace (initial temperature: 25℃, heating time: 140min, holding temperature: 700℃, holding time: 120min, initial cooling temperature: 700℃, cooling time: 140min, final sampling temperature: 25℃). After placing seven poplar wood blocks into the tube furnace, connect the tube furnace, and fill it with nitrogen gas, slowly increasing the pressure valve from 0MPa to 0.05MPa. Release the pressure and slowly reduce it to 0MPa. After the air in the tube furnace is exhausted, start the tube furnace. The tube furnace will carbonize the sample according to the set program. When "STOP" is displayed on the screen, it indicates that the carbonization is complete. First, turn off the nitrogen gas. After the nitrogen in the furnace is exhausted, turn off the instrument. The carbonization process is complete, and the sample can be removed.

[0040] S2. Label two 50mL beakers A and B respectively. Weigh 0.07g FeCl2·4H2O and 0.20g FeCl3·6H2O using an electronic balance. Add 20mL of deionized water to beaker A, then add the remaining 0.07g FeCl2·4H2O and 0.20g FeCl3·6H2O to beaker A and stir until completely dissolved. Next, add 0.20g monolayer graphene and 20mL anhydrous ethanol to beaker B and stir until homogeneous. Pour the solution from beaker A into beaker B and mix thoroughly. Place a magnet in beaker B and stir magnetically for 30 minutes. After stirring, adjust the pH of the solution to 10 with ammonia. Collect the composite Fe3O4@Graphene nanoparticles using a magnet, wash them several times with deionized water, and then dry them in a forced-air drying oven for later use.

[0041] S3. Weigh 0.1g of Fe3O4@Graphene nanoparticles and pour 100mL of deionized water into a 500mL beaker. Add the weighed Fe3O4@Graphene nanoparticles to the beaker, place a magnetic stir bar in the beaker, and put the beaker on a magnetic stirrer. After turning on the stir bar, stir the Fe3O4@Graphene solution magnetically. Then, put five pieces of carbonized poplar wood into the Fe3O4@Graphene solution and stir magnetically to impregnate them. Take out the impregnated samples at 1h, 2h, 3h, 4h, and 5h.

[0042] S4. Unimpregnated carbonized wood and carbonized wood impregnated for 1h, 2h, 3h, 4h, and 5h were electroless plated with Ni. The Ni-plated samples were named CWN-1, CWN-2, CWN-3, CWN-4, and CWN-5, respectively. Unimpregnated carbonized wood was named CWN, and carbonized wood served as a control group and was named CW.

[0043] The method for electroless nickel plating is as follows:

[0044] (1) Preparation of activation solution A: Add 400mL of distilled water to a beaker; add 4.8mL of concentrated hydrochloric acid to the beaker, stir with a glass rod, then add 6g of nickel sulfate granules, pour into the beaker, and stir with a glass rod until completely dissolved.

[0045] (2) Preparation of activation solution B: Add 400mL of distilled water to a beaker; weigh 4.8g of sodium hydroxide and stir until dissolved; then add 6g of sodium borohydride and stir with a glass rod until completely dissolved.

[0046] (3) Preparation of electroless nickel plating solution: Add 600mL of distilled water to a beaker; weigh 19.8g of nickel sulfate and add it, stirring to dissolve; weigh 18g of sodium citrate and add it, stirring to dissolve; weigh 16.8g of sodium hypophosphite and add it, stirring to dissolve; weigh 20mg of thiourea and add it, stirring until dissolved; add ammonia to adjust the pH of the solution to 9-9.5.

[0047] (4) Place the sample in activation solution A for 15 min, turn the sample over once every 5 min, take it out, and when there is no liquid dripping from the sample, place it in activation solution B for 90 s seconds, turn the sample over once every 30 seconds, take it out, and let it stand until there is no liquid dripping from the surface; then place the sample in chemical nickel plating solution at 60℃ for chemical nickel plating treatment, and turn the sample over once every 3 min during the nickel plating process.

[0048] S5. Place all samples in the waveguide for electromagnetic shielding testing.

[0049] Example 2

[0050] This embodiment provides a method for preparing a conductive and magnetic carbonized wood-based electromagnetic shielding material. The only difference from Embodiment 1 is that in S2, the weights of graphene, FeCl2·4H2O, and FeCl3·6H2O are changed to 3:1:1, i.e., 0.60g of graphene, while the weights of FeCl2·4H2O and FeCl3·6H2O remain unchanged.

[0051] Example 3

[0052] This embodiment provides a method for preparing a conductive and magnetic carbonized wood-based electromagnetic shielding material. The only difference from Embodiment 1 is that in S2, the weights of graphene, FeCl2·4H2O, and FeCl3·6H2O are changed to 1:3:3, that is, the weight of graphene remains unchanged, while the weights of FeCl2·4H2O and FeCl3·6H2O are 0.21g and 0.6g, respectively.

[0053] The Fe3O4@Graphene nanoparticles prepared in Examples 2 and 3 by varying their content exhibit different electromagnetic properties, resulting in different electromagnetic properties and shielding effectiveness of the carbonized wood-based electromagnetic shielding materials. Therefore, the composites prepared by varying the content also fall within the scope of this study.

[0054] Tests have shown that, for example Figure 2As shown, the electromagnetic shielding material prepared in Example 1 exhibits excellent conductivity. The conductivity of the sample impregnated with Fe3O4@Graphen solution for 1 hour reaches a maximum of 631.3 S / cm. Compared to other samples impregnated for different times, the significantly higher conductivity of CWN-1 is due to the intense aggregation of Fe3O4@Graphen nanoparticles at the beginning of impregnation, resulting in locally aggregated Fe3O4@Graphen nanoparticles in the 1-hour impregnation sample. Subsequently, the concentration of Fe3O4@Graphen nanoparticles decreases, and the aggregation weakens. The locally high conductivity explains the generally high overall conductivity of the 1-hour impregnation sample, which is reasonable. Magnets can easily attract the composite material without it falling off. Figure 3 The result indicates that the composite material has good magnetic properties.

[0055] like Figure 4 As shown, the electromagnetic shielding effectiveness of CNW-5 composite material can reach 70dB in the frequency range of 8.2 to 12.4 GHz, and can reach 80dB in some frequency bands, indicating that it has excellent electromagnetic shielding performance.

[0056] In Example 1 of this invention, a composite material was prepared by electroless nickel plating after impregnating Fe3O4@Graphene nanoparticles onto the surface of carbonized wood. The carbonized wood composite material prepared by this method exhibits excellent electromagnetic shielding performance. The carbonization temperature was set at 700℃, but it is not limited to 700℃; a carbonization temperature fluctuating within this range is also acceptable. Impregnating the surface of carbonized wood with Fe3O4@Graphene nanoparticles can increase the electromagnetic properties of the carbonized wood surface. This is because graphene has excellent electrical conductivity, and iron(III) oxide has good magnetic properties. The composite nanoparticles, combined with the carbonized wood, impart electromagnetic properties. After electroless plating, the Fe3O4@Graphene nanoparticles are tightly bonded to and dispersed within the plating layer, thus achieving the excellent electromagnetic shielding performance of the composite material.

[0057] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0058] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a carbonized wood-based electromagnetic shielding material with electrical and magnetic conductivity, characterized in that, It is prepared by high-temperature carbonization of wood, followed by impregnation of Fe3O4@Graphene nanoparticles on its surface, and finally electroless nickel plating; Specifically, the following steps are included: S1. Cut and process the scar-free virgin wood into wood blocks, and then put them into a tube furnace for carbonization. After carbonization, screen out flat and crack-free carbonized wood blocks for later use. The carbonization process includes: turning on the tube furnace, powering on the vacuum pump, setting the program for the tube furnace, placing the wood block into the tube furnace, connecting the tube furnace, filling with nitrogen, slowly increasing the pressure valve from 0 MPa to 0.05 MPa, then releasing the pressure and slowly reducing it to 0 MPa. After the air in the tube furnace is exhausted, start the tube furnace. The tube furnace carbonizes the sample according to the set program. When "STOP" is displayed on the screen, it indicates that the carbonization is complete. First, turn off the nitrogen. After the nitrogen in the furnace is exhausted, turn off the instrument. The carbonization process is complete. The parameters of the tube furnace are as follows: initial temperature: 25℃, heating time: 140min, holding temperature: 700℃, holding time: 120min, initial cooling temperature: 700℃, cooling time: 140min, and final sampling temperature: 25℃. S2. Place FeCl2·4H2O, FeCl3·6H2O and water in container A and stir until completely dissolved. Then place monolayer graphene and anhydrous ethanol in container B and stir evenly. Pour the solution from container A into container B and mix evenly. After stirring magnetically for a period of time, adjust the pH of the solution to 10 to obtain Fe3O4@Graphene nanoparticles. Collect the Fe3O4@Graphene nanoparticles with a magnet, wash and dry them for later use. S3. Fe3O4@Graphene nanoparticles and water are placed in a container and magnetically stirred. During the stirring process, carbonized wood blocks from S1 are added and stirred for impregnation. After impregnation for a period of time, the sample is taken out. The amount of Fe3O4@Graphene nanoparticles added is 0.1-0.5 g, and the amount of water added is 100-500 mL. S4. The sample obtained in S3 is subjected to chemical nickel plating to obtain the conductive and magnetic carbonized wood-based electromagnetic shielding material.

2. The method for preparing a conductive and magnetically permeable carbonized wood-based electromagnetic shielding material according to claim 1, characterized in that, In S1, the specifications of the wooden block are: 5-7cm in length, 2.5-3cm in width, and 0.4-0.5cm in thickness.

3. The method for preparing a conductive and magnetically permeable carbonized wood-based electromagnetic shielding material according to claim 1, characterized in that, In S2, the amount of FeCl2·4H2O added is 0.07g, the amount of FeCl3·6H2O added is 0.20g, the amount of water added is 20mL, the amount of monolayer graphene added is 0.20g, and the amount of anhydrous ethanol added is 20mL.

4. The method for preparing a conductive and magnetically permeable carbonized wood-based electromagnetic shielding material according to claim 1, characterized in that, In S2, the magnetic stirring time is 30-60 min, and the stirring speed is 100-300 rpm; the pH of the solution is adjusted by using ammonia.

5. The method for preparing a conductive and magnetically permeable carbonized wood-based electromagnetic shielding material according to claim 1, characterized in that, In S3, the soaking time is 1h, 2h, 3h, 4h or 5h.

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