Preparation method of carbonized wood chemical copper-plated electromagnetic shielding material

Abstract

The application discloses a method for preparing carbonized wood composite material with electromagnetic shielding efficiency. The method is through carbonization, activation, and then chemical copper plating treatment of the carbonized wood, so that the carbonized wood is endowed with good electromagnetic shielding characteristics. The contact angle of the carbonized wood can reach 126.2 degrees, and the carbonized wood has good hydrophobic characteristics. After the carbonized wood is subjected to chemical copper plating for 6 minutes, the surface roughness of the carbonized wood can be as small as 7.62 microns, the conductivity of the carbonized wood subjected to chemical copper plating for 12 minutes is 240.5 S / cm, and in the frequency range of 8.2 to 12.4 GHz, the average electromagnetic shielding efficiency of the carbonized wood can reach 51.82 dB.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, and more particularly to a preparation method of a carbonized wood chemical copper-plated electromagnetic shielding material. BACKGROUND

[0002] With the miniaturization and high integration of electronic devices, the electromagnetic environment that humans live in is becoming increasingly complex. Electromagnetic radiation can have certain negative effects on the human body, such as headaches, insomnia, fatigue, and other health problems. In recent years, multi-layer and multi-layer structure electromagnetic shielding materials have received extensive attention. These new materials have superior shielding performance and can effectively block the propagation of electromagnetic radiation. Compared with traditional single-layer materials, multi-layer electromagnetic shielding materials can better absorb and reflect electromagnetic waves, thereby effectively protecting the human body from radiation damage. Multi-layer structure electromagnetic shielding materials are mainly achieved through the combination of two layers of different materials.

[0003] Carbonized wood is a kind of wood that has been calcined, which has the characteristics of no pollution, easy preparation, excellent performance, etc., and is a cost-effective material. At the same time, carbonized wood is easy to modify and can be loaded with metal ions. After depositing copper (Cu) on the surface, carbonized wood can form a composite material that has electromagnetic shielding and photocatalytic properties. Since carbonized wood is naturally composed of multiple chemical components and multiple cells, it has the advantages of high strength-to-weight ratio, good heat and sound insulation, low processing energy consumption, low environmental pollution, renewability, and natural degradation, etc., and therefore becomes an ideal substrate for preparing green and efficient shielding materials.

[0004] Currently, electromagnetic shielding materials mainly use reflection processes to reduce the absorption of electromagnetic waves. Shielding bodies usually use mobile charge carriers (such as electrons or holes) to interact with electromagnetic fields in the radiation field. In the field of electromagnetic interference shielding, copper is often used to improve the shielding effect of carbonized wood. This composite material has great potential and broad application prospects in the preparation of green and efficient shielding materials. SUMMARY

[0005] Therefore, the present application provides a preparation method of a carbonized wood chemical copper-plated electromagnetic shielding material.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] A preparation method of a carbonized wood chemical copper-plated electromagnetic shielding material, comprising the following steps:

[0008] (1) Put a cuboid wood into a furnace and carbonize it under the condition of nitrogen to obtain carbonized wood, which is ready for use;

[0009] (2) polishing the surface of the carbonized wood to make it smooth, to obtain carbonized wood blocks;

[0010] (3) performing a first chemical copper plating treatment on the carbonized wood blocks (the method of chemical copper plating is specifically referred to in patent ZL201810622330.2), to obtain the electromagnetic shielding material.

[0011] Preferably, the size of the cuboid wood in step (1) is 6-7 cm in length, 2.5-3 cm in width, and 0.5-1 mm in thickness.

[0012] Preferably, the carbonization in step (1) specifically comprises: placing the cuboid wood into a tubular furnace filled with nitrogen, then slowly increasing the temperature to 700℃ at a certain heating rate, maintaining the stable temperature for 2 h, then gradually reducing the temperature to room temperature, and screening out the carbonized wood that is flat and free of cracks for standby use.

[0013] Preferably, step (3) adopts glass rod stirring during the first chemical copper plating treatment, the stirring time is 5-10 min, the stirring speed is 50-80 times / min, and the carbonized wood blocks are turned over every 1 min.

[0014] Preferably, step (3) further comprises a second chemical copper plating treatment (the method of chemical copper plating is specifically referred to in patent ZL201810622330.2), specifically: placing the carbonized wood blocks after the first chemical copper plating treatment into the copper plating solution, then adding 3-5 drops of NaOH solution with a mass concentration of 25%, stirring with a glass rod during the period, the stirring time is 3-8 min, the stirring speed is 60-100 times / min, and the carbonized wood blocks are turned over every 1 min.

[0015] The chemical copper plating treatment specifically comprises:

[0016] Take three 500 mL beakers, add 200 mL distilled water into the first beaker and mark it as A, add 200 mL distilled water into the second beaker and mark it as B, and add 160 mL distilled water into the third beaker and mark it as C; slowly pour 2.4 mL of concentrated hydrochloric acid into A while stirring, then add 3 g of copper sulfate, and stir until there are no copper sulfate particles at the bottom, to obtain the activation solution A;

[0017] Slowly pour 2.4 g of sodium hydroxide into beaker B, slowly stir until the sodium hydroxide is completely dissolved, then add 3 g of sodium borohydride, and stir until the sodium borohydride is completely dissolved, to obtain the activation solution B;

[0018] C is placed in a 60℃ constant temperature water bath for preheating 15min, then copper sulfate 12g, potassium sodium tartrate 3g, EDTA·disodium salt 4g, potassium ferrocyanide 0.45g, 10mL formaldehyde are added in turn, after stirring and dissolving uniformly, the mass fraction of 25% sodium hydroxide solution is used to adjust the pH value of the plating solution to 12, and the chemical plating Cu plating solution is obtained;

[0019] The carbonized wood block is placed in the activation liquid A for activation for 15min, the wood sheet is turned over once every 5min with a steel tweezers, and then taken out, when no liquid drops from the carbonized wood, the carbonized wood is placed in the activation liquid B for activation for 90 seconds, the carbonized wood is turned over once every 30 seconds with a tweezers, and then taken out, when no liquid drops from the carbonized wood, the carbonized wood is placed in the Cu chemical plating liquid, and Cu chemical plating is carried out at pH = 12 and a temperature of 60°.

[0020] It can be known from the technical solutions that, compared with the prior art, the present application has the following beneficial effects:

[0021] 1. In the frequency range of 8.2 to 12.4GHz, the electromagnetic shielding effectiveness of the composite material can be adjusted according to different chemical copper plating time and chemical copper plating times, and according to the specific chemical copper plating time and chemical copper plating times, the carbonized wood composite material with shielding effectiveness in the range of 30-55dB can be prepared;

[0022] 2. The composite material prepared by chemical copper plating on the surface of carbonized wood has excellent electrical conductivity, and the electrical conductivity can reach 240.5S / cm and 377.24S / cm respectively;

[0023] 3. The contact angle of the carbonized wood can reach 126.2°, and the carbonized wood has electrical conductivity and electromagnetic shielding effectiveness, and the electrical conductivity and electromagnetic shielding effectiveness are 0.1S / cm and 30dB respectively;

[0024] 4. The carbonized wood chemical copper plating has good flame retardant performance, and no ignition phenomenon occurs when it is placed under an alcohol lamp for 45s;

[0025] 5. The carbonized wood prepared by the method has fiber structure, carbon structure and porous structure, and is an ideal multi-layer electromagnetic shielding and electromagnetic attenuation template material. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0027] Figure 1A flow chart of a preparation method of a carbonized wood chemical copper-plated electromagnetic shielding material according to an embodiment of the present application;

[0028] Figure 2 A laser confocal microscope morphology of the carbonized wood electromagnetic shielding material after chemical copper plating only once according to the present application, wherein a: chemical copper plating for 2 min, c: chemical copper plating for 4 min, e: chemical copper plating for 6 min, g: chemical copper plating for 8 min, i: chemical copper plating for 10 min, k: chemical copper plating for 12 min are surface morphology diagrams; b-l: 3D diagrams of chemical Cu plating time being 2, 4, 6, 8, 10, and 12 min, respectively;

[0029] Figure 3 A laser confocal microscope morphology of the carbonized wood electromagnetic shielding material after secondary chemical copper plating according to the present application, wherein a: chemical copper plating for 2 min, c: chemical copper plating for 4 min, e: chemical copper plating for 6 min, g: chemical copper plating for 8 min, i: chemical copper plating for 10 min, k: chemical copper plating for 12 min are surface morphology diagrams; b-l: 3D diagrams of chemical Cu plating time being 2, 4, 6, 8, 10, and 12 min, respectively;

[0030] Figure 4 A SEM morphology of the carbonized wood electromagnetic shielding material after chemical copper plating only once according to the present application, wherein a: chemical copper plating for 2 min, c: chemical copper plating for 4 min, c: chemical copper plating for 6 min, d: chemical copper plating for 8 min, e: chemical copper plating for 10 min, f: chemical copper plating for 12 min;

[0031] Figure 5 A SEM morphology of the carbonized wood electromagnetic shielding material after secondary chemical copper plating according to the present application, wherein a: chemical copper plating for 2 min, c: chemical copper plating for 4 min, c: chemical copper plating for 6 min, d: chemical copper plating for 8 min, e: chemical copper plating for 10 min, f: chemical copper plating for 12 min;

[0032] Figure 6 A surface scanning electron microscope element content of the carbonized wood electromagnetic shielding material after secondary chemical copper plating according to the present application;

[0033] Figure 7 A cross-section scanning electron microscope element content of the carbonized wood electromagnetic shielding material after secondary chemical copper plating according to the present application;

[0034] Figure 8 A cross-section scanning electron microscope morphology of the carbonized wood according to the present application;

[0035] Figure 9 A conductivity vs. chemical Cu plating time diagram of the carbonized wood electromagnetic shielding material according to the present application;

[0036] Figure 10 A hydrophobicity performance analysis diagram;

[0037] Figure 11 Flame retardant test for 8 min copper plating;

[0038] Figure 12 The electromagnetic shielding effectiveness diagram of the wood-based electromagnetic shielding material obtained by the embodiment of the present application. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0040] Embodiment 1

[0041] The embodiment provides a preparation method of a carbonized wood chemical copper plating electromagnetic shielding material, comprising the following steps:

[0042] (1) Put the cuboid single board wood with a length of 6-7 cm, a width of 2.5-3 cm and a thickness of 0.5-1 mm into a tube furnace filled with nitrogen, then raise the temperature to 700 DEG C and keep the stable temperature for 2 hours, then gradually reduce the temperature to room temperature, take out the carbonized wood, and screen out the carbonized wood which is flat and has no cracks for standby;

[0043] (2) Gently polish the surface of the carbonized wood single board by using sandpaper to make it smooth, and obtain the carbonized wood single board in the shape of a cuboid;

[0044] (3) Perform a chemical copper plating treatment on the carbonized wood (for a method of chemical copper plating, refer to patent ZL201810622330.2), and stir by using a glass rod during the chemical copper plating treatment, the stirring time is 5-10 min, the stirring speed is 50-80 times / min, and the carbonized wood is turned over every 1 min;

[0045] (4) Second copper plating treatment: place the carbonized wood after the first chemical copper plating treatment in a copper plating solution, then add a few drops of NaOH solution, stir by using a glass rod during the process, the stirring time is 3-8 min, the stirring speed is 60-100 times / min, and the carbonized wood is turned over every 1 min.

[0046] The chemical copper plating treatment specifically comprises:

[0047] Take three 500mL beakers, add 200mL of distilled water to the first beaker (labeled A), add 200mL of distilled water to the second beaker (labeled B), and add 160mL of distilled water to the third beaker (labeled C). Slowly pour 2.4mL of concentrated hydrochloric acid into beaker A while stirring. Then add 3g of copper sulfate and stir until there are no copper sulfate particles at the bottom. This will give activation solution A.

[0048] Slowly pour 2.4g of sodium hydroxide into beaker B and stir slowly until the sodium hydroxide is completely dissolved. Then add 3g of sodium borohydride and stir until the sodium borohydride is completely dissolved to obtain activation solution B.

[0049] Place C in a constant temperature water bath at 60°C and preheat for 15 minutes, then add 12 g of copper sulfate, 3 g of potassium sodium tartrate, 4 g of EDTA·disodium salt, 0.45 g of potassium ferrocyanide, and 10 mL of formaldehyde in sequence, stir and dissolve evenly, and adjust the pH value of the plating solution to 12 with the 25% mass fraction sodium hydroxide solution to obtain an electroless Cu plating solution;

[0050] The carbonized wood was placed in activation solution A for activation for 15 minutes. The thin wood slice was turned over once with tempered tweezers every 5 minutes and taken out. When no liquid dripped from the carbonized wood, it was placed in activation solution B for activation for 90 seconds. The carbonized wood was turned over once with tweezers every 30 seconds and taken out. When no liquid dripped from the carbonized wood, it was placed in a Cu chemical plating solution and chemically plated with Cu at pH = 12 and a temperature of 60°.

[0051] The samples were prepared and then subjected to characterization tests.

[0052] like Figure 2 and Figure 3 As shown ( Figure 3 In the experiment, the time of the first copper plating is kept constant and only the time of the second copper plating is changed. The surface morphology of the carbonized wood measured by the laser co-polymerization microscope after different times of chemical copper plating is very different. Figure 2 It can be seen that the roughness stereogram of 1-6 is the smoothest, and the surface roughness reaches 4.64μm. Figure 3 The relatively flat wood surface in the stereogram is 2-2, and its roughness is 5.13μm. Experimental data proves that after the carbonized wood is electrolessly plated with Cu, the surface structure of the sample tends to become irregular. As the number and time of copper plating increase, the overall surface roughness of the sample gradually increases. At the same time, from the surface morphology in the figure, it can be seen that the inherent surface morphology of the carbonized wood gradually disappears. As the metal accumulation becomes more dense, the carbonized wood surface is gradually covered by metal, the tightness between particles increases, and the overall trend of increasing surface roughness is obvious. This further illustrates that as the time and number of electroless Cu plating increase, the surface of the composite material tends to become rough, mainly due to the increase in copper particles.

[0053] likeFigure 4 and Figure 5 As shown ( Figure 5 In the experiment, the time of the first copper plating was kept constant and only the time of the second copper plating was changed. The surface metal accumulation of the first copper plating for 5 minutes was relatively sparse and irregular. The pores of the surface metal were also relatively large, and a clearer wood texture could be seen. However, with the increase of the number of chemical copper plating times and the increase of the chemical copper plating time, the surface adhesion of the metal copper became better and better. It can be clearly seen from the SEM electron microscope image that the metal accumulation arrangement became more and more dense, the arrangement became more and more regular, and the pores were significantly reduced. When the chemical Cu plating time was 1-12 minutes, Cu was evenly distributed in the chemically plated metal layer on the surface of the carbonized wood (porous carbon material), and the gaps between the metal atoms were small. When a large amount of metal copper was accumulated on the surface of the carbonized wood, it affected the surface roughness of the wood, further reflecting the conclusion of the laser confocal microscope.

[0054] like Figure 6 and Figure 7 As shown, the main component of the carbonized wood surface and cross-section is metallic copper.

[0055] like Figure 8 As shown, the method of this patent can successfully prepare carbonized wood with fiber structure, carbon structure and porous structure, which is an ideal template material for multi-level electromagnetic shielding, electromagnetic attenuation and absorption of electromagnetic waves.

[0056] like Figure 9 As shown, the composite material has excellent electrical conductivity. The conductivity of the single electroless Cu plating increases with the extension of the electroless plating time. The conductivity rises significantly in the 8-10 minute range; the conductivity rises more slowly in the 4-6 minute range; and the conductivity shows a more obvious upward trend in the 8-12 minute range, which then gradually becomes a gentle increase. The conductivity of the secondary electroless copper plating increases by 64.76 S / cm with an increase in the copper plating time from 2 to 12 minutes. The maximum conductivity reaches 377.24 S / cm in the 2-12 minute range, and it shows a gentle increase in many places. In the 2-4 minute range, the conductivity of the sample only increases by 19.4 S / cm.

[0057] like Figure 10 As shown in the figure, before the electroless plating treatment, the carbonized wood showed good hydrophobicity, with contact angles of 126.2° and 127.4°, respectively, indicating that the carbonized wood has good hydrophobicity. However, in the composite material after the electroless plating treatment, there is almost no contact angle, approximately equal to 0°, indicating that the carbonized wood after the electroless plating treatment exhibits good hydrophilicity. This result is because after the electroless plating treatment, part of the structure of the carbonized wood surface is destroyed by the activation treatment, making the pores of the carbonized wood larger. The plated metal does not completely cover the carbonized wood surface, so the hydrophobicity is not good.

[0058] like Figure 11 The figure shows the flame retardant test of copper plating for 8 minutes.

[0059] like Figure 12 The figure shows the electromagnetic shielding effectiveness of chemical copper plating on carbonized wood in the frequency range of 8.2MHz to 12..4GHz (X-band). The average electromagnetic shielding effectiveness can reach 51.82dB. Chemical copper plating on the surface of carbonized wood can be used to prepare an ideal electromagnetic shielding material.

[0060] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0061] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one 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 present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a carbonized wood chemical copper-plated electromagnetic shielding material, characterized in that: The following steps are involved: (1) placing a rectangular block of wood into a furnace and carbonizing it under nitrogen to obtain carbonized wood for later use; the rectangular block of wood has a length of 6-7 cm, a width of 2.5-3 cm, and a thickness of 0.5-1 mm; the rectangular block of wood is poplar; (2) polishing the surface of the carbonized wood to make it smooth, thereby obtaining a carbonized wood block; (3) performing a chemical copper plating treatment on the carbonized wood block to obtain the electromagnetic shielding material; The carbonization in step (1) specifically includes: placing the rectangular wood into a nitrogen-filled tubular furnace, then raising the temperature to 700° C. and maintaining a stable temperature for 2 hours, then gradually lowering the temperature to room temperature, taking out and screening out the flat and crack-free carbonized wood for later use; During the chemical copper plating process, a glass rod is used for stirring, the stirring time is 5-10 minutes, the stirring speed is 50-80 times / min, and the carbonized wood block is turned over once every 1 minute.

2. The method for preparing a carbonized wood chemical copper-plated electromagnetic shielding material according to claim 1, characterized in that: Step (3) also includes a secondary chemical copper plating treatment, specifically: placing the carbonized wood block after the primary chemical copper plating treatment in a copper plating solution, and then adding 3-5 drops of a 25% mass concentration of NaOH solution, stirring with a glass rod during the process, the stirring time is 3-8 minutes, the stirring rate is 60-100 times / min, and the carbonized wood block is turned over once every 1 minute.

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