A preparation method and material of biomass carbon / silver composite electromagnetic shielding material

Abstract

The invention relates to the technical field of shielding materials, and to a preparation method and material of a biomass carbon / silver composite electromagnetic shielding material, comprising: using hexadecyl trimethyl ammonium bromide solution to treat wood materials, and carbonizing the wood materials after the treatment to obtain biomass carbon; using hydrochloric acid solution, trishydroxymethylaminomethane solution and dopamine hydrochloride to prepare dopamine monomer solution, and using hydrogen peroxide solution and the prepared dopamine monomer solution to modify biomass carbon to obtain polydopamine-modified biomass carbon; using silver nitrate solution and ammonia solution to prepare silver ammonia solution, and immersing polydopamine-modified biomass carbon in the silver ammonia solution, adjusting the pH value of the silver ammonia solution, adding glucose solution, and ultrasonically reacting to obtain biomass carbon / silver composite electromagnetic shielding material. The invention can deposit silver nanoparticles on the surface and internal pores of biomass carbon modified by polydopamine, and has excellent electromagnetic shielding capabilities in both dual bands.

Description

Technical Field

[0001] The invention relates to the technical field of shielding materials, and in particular to a preparation method of a biomass carbon / silver composite electromagnetic shielding material and materials thereof. Background Art

[0002] With the continuous development of science and technology, electromagnetic pollution has been considered the fourth largest public hazard after air pollution, water pollution and noise pollution. Electromagnetic radiation not only affects the normal operation of precision electronic equipment, but also threatens human health. At the same time, the rapid popularization of modern telecommunications technology represented by 5G has promoted the improvement of electromagnetic shielding (EMI) materials and equipment.

[0003] Electromagnetic shielding materials mainly include metal, filling, surface coating and conductive coating. Traditional metal-based materials show excellent electromagnetic interference shielding effects due to their high electrical conductivity, but they are gradually replaced by other materials due to their high price, ultra-high density, poor environmental resistance and other disadvantages. It is more important to explore lighter and lower-cost electromagnetic shielding materials. Biomass carbon electromagnetic shielding materials are widely available and low-cost. In recent years, wood resources have been widely studied for their sustainability, light weight, porous layered structure, and abundant resources. However, wood materials are insulating materials with poor electrical conductivity and cannot achieve the effect of electromagnetic interference shielding. In the prior art, when wood materials are compounded with metal materials, it is easy to have problems such as the metal material coating being loose and unevenly distributed, and the inability to give full play to the advantages of both and the inability to achieve electromagnetic shielding effects in multiple bands at the same time.

[0004] Therefore, how to effectively compound wood-based materials with other conductive materials, give full play to the advantages of each component of the composite material, achieve excellent electromagnetic shielding effects in multiple bands, and ensure the maximization of electromagnetic shielding efficiency has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of this, in order to overcome the deficiencies of the prior art, the present invention provides a method for preparing a biomass carbon / silver composite electromagnetic shielding material and the material thereof.

[0006] In one aspect, the present invention provides a method for preparing a biomass carbon / silver composite electromagnetic shielding material, the method comprising:

[0007] Step 1: Biomass carbon preparation

[0008] The wood material is activated by using a hexadecyltrimethylammonium bromide solution, and the activated wood material is carbonized to obtain biomass carbon;

[0009] Step 2: Preparation of polydopamine-modified biomass carbon

[0010] A dopamine monomer solution is prepared by using a hydrochloric acid solution, a tris(hydroxymethyl)aminomethane) solution and dopamine hydrochloride according to a ratio, and a hydrogen peroxide solution and the prepared dopamine monomer solution are used to modify the biomass carbon according to a ratio to obtain a polydopamine-modified biomass carbon;

[0011] Step 3: Preparation of biomass carbon / silver composite electromagnetic shielding material

[0012] Silver nitrate solution and ammonia solution are used to prepare a silver ammonia solution according to a ratio, and the polydopamine-modified biomass carbon is immersed in the prepared silver ammonia solution. After the pH value of the silver ammonia solution is adjusted, a glucose solution is added, and an ultrasonic reaction is performed to obtain a biomass carbon / silver composite electromagnetic shielding material.

[0013] Preferably, in the preparation method of the biomass carbon / silver composite electromagnetic shielding material of the present invention, in step one, a hexadecyltrimethylammonium bromide solution is used to perform an active treatment on the wood material, including: ultrasonically immersing the wood material in a hexadecyltrimethylammonium bromide solution with a concentration of 0.03-0.1 mol / L for 30 minutes, washing the wood material after ultrasonic immersion with deionized water, and drying the washed wood material at 60°C for 24 hours.

[0014] Preferably, in the method for preparing the biomass carbon / silver composite electromagnetic shielding material of the present invention, in step 1, the carbonization treatment comprises: heating to 700-900°C at a heating rate of 5°C / min, keeping the temperature for 3h, and naturally cooling to room temperature.

[0015] Preferably, in the preparation method of the biomass carbon / silver composite electromagnetic shielding material of the present invention, in step 2, a dopamine monomer solution is prepared by using a hydrochloric acid solution, a tris(hydroxymethyl)aminomethane solution and dopamine hydrochloride according to a ratio, comprising: sequentially adding a hydrochloric acid solution and dopamine hydrochloride to a tris(hydroxymethyl)aminomethane solution, wherein the concentration of the hydrochloric acid solution is 1 mol / L, the concentration of the tris(hydroxymethyl)aminomethane solution is 0.4 mol / L, the molar ratio of the hydrochloric acid solution, the tris(hydroxymethyl)aminomethane solution and the dopamine hydrochloride is 1:1.2:0.0316, and magnetic stirring is performed at room temperature for 10 minutes to obtain a dopamine monomer solution.

[0016] Preferably, in the preparation method of the biomass carbon / silver composite electromagnetic shielding material of the present invention, in step 2, the biomass carbon is modified by using a hydrogen peroxide solution and a prepared dopamine monomer solution according to a ratio, including: soaking the biomass carbon in a dopamine monomer solution, and adding a hydrogen peroxide solution to the dopamine monomer solution at a dropping speed of 0.02 ml / s, wherein the concentration of the hydrogen peroxide solution is 0.043 mol / L, and the volume ratio of the hydrogen peroxide solution to the dopamine monomer solution is 1:35.

[0017] Preferably, in the method for preparing the biomass carbon / silver composite electromagnetic shielding material of the present invention, in step 2, after the hydrogen peroxide solution is added dropwise, the biomass carbon is soaked for 24 hours, and the biomass carbon is turned over every 4 hours.

[0018] Preferably, the preparation method of the biomass carbon / silver composite electromagnetic shielding material of the present invention, step three, comprises: adding 0.1 mol / L silver nitrate solution to 5% wt ammonia solution at a volume ratio of 5:2 to prepare a silver ammonia solution, soaking the polydopamine-modified biomass carbon in the prepared silver ammonia solution, using 0.1 mol / L citric acid solution to adjust the pH value of the silver ammonia solution soaked with polydopamine-modified biomass carbon to 10, adding 0.2 mol / L glucose solution, and ultrasonically reacting for 30-60 minutes to obtain a biomass carbon / silver composite electromagnetic shielding material.

[0019] Preferably, in the method for preparing the biomass carbon / silver composite electromagnetic shielding material of the present invention, in step three, the volume ratio of the glucose solution to the silver nitrate solution is 1:1.

[0020] Preferably, in the method for preparing the biomass carbon / silver composite electromagnetic shielding material of the present invention, in step three, during the ultrasonic reaction, the polydopamine-modified biomass carbon is turned over every 5 minutes.

[0021] On the other hand, the present invention provides a biomass carbon / silver composite electromagnetic shielding material, which is prepared according to the above method.

[0022] The preparation method of the biomass carbon / silver composite electromagnetic shielding material and the material thereof of the present invention have the following beneficial effects:

[0023] 1. The wood material is activated by using hexadecyltrimethylammonium bromide solution before carbonization, so that more favorable functional group inheritance can be obtained before carbonization, avoiding the deficiency caused by the inertness of the surface of the material after carbonization, so that the surface of the biomass carbon material after carbonization is positively charged, and due to the electrostatic adsorption of the positive charge, the effective combination of the biomass carbon material and dopamine is promoted;

[0024] 2. The polydopamine layer is formed by adhering dopamine monomers to the cell channels of carbonized wood, and hydrogen peroxide is added during the formation process to reduce the time for forming the polydopamine layer, thereby ensuring that a polydopamine film layer with uniform thickness is obtained in a short time;

[0025] 3. By depositing silver nanoparticles on the surface and internal pores of biomass carbon modified with polydopamine, the wood material and the conductive silver particles are effectively combined. The vertically cut wood blocks carbonized at 800°C for 3 hours have an electromagnetic shielding performance of 59.6-64.7 dB in the X-band and 83.9-104.9 dB in the Ka-band. They have excellent electromagnetic shielding capabilities in both bands and can meet the application requirements of dual-band electromagnetic shielding materials at the same time. The shielding efficiency reaches 99.99%;

[0026] 4. The preparation method of the biomass carbon / silver composite electromagnetic shielding material of the present invention has the advantages of being safe, reliable and pollution-free. The prepared biomass carbon / silver composite electromagnetic shielding material has the characteristics of being anti-corrosive, moisture-proof, antibacterial and having efficient electromagnetic shielding performance, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 This is a SEM morphology image of the cross section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 1 of the present invention;

[0029] Figure 2 This is a SEM morphology image of a cross section of a biomass carbon / silver composite electromagnetic shielding material prepared in Example 2 of the present invention;

[0030] Figure 3 This is a SEM morphology image of the cross section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 3 of the present invention;

[0031] Figure 4 This is a SEM morphology image of a cross section of a biomass carbon / silver composite electromagnetic shielding material prepared in Example 4 of the present invention;

[0032] Figure 5 This is a SEM morphology image of a cross section of a biomass carbon / silver composite electromagnetic shielding material prepared in Example 5 of the present invention;

[0033] Figure 6 This is a SEM morphology image of a cross section of a biomass carbon / silver composite electromagnetic shielding material prepared in Example 6 of the present invention;

[0034] Figure 7 This is a graph showing the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 3 of the present invention in the X-band;

[0035] Figure 8 This is a graph showing the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 4 of the present invention in the X-band;

[0036] Fig. 9 This is a graph showing the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 5 of the present invention in the X-band;

[0037] Fig.10 This is a diagram of the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 3 of the present invention in the Ka band;

[0038] Fig.11 This is a diagram of the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 4 of the present invention in the Ka band. DETAILED DESCRIPTION

[0039] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0040] It should be noted that the following embodiments and features in the embodiments may be combined with each other in the absence of conflict; and, based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making any creative work are within the scope of protection of the present disclosure.

[0041] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein may be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein may be implemented independently of any other aspect, and two or more of these aspects may be combined in various ways. For example, any number of aspects described herein may be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein may be used to implement this device and / or practice this method.

[0042] Example 1

[0043] Preparation of biomass carbon / silver composite electromagnetic shielding materials:

[0044] Step 1: Biomass carbon preparation

[0045] The wood material cut perpendicular to the wood growth direction was ultrasonically soaked in a 0.03 mol / L hexadecyltrimethylammonium bromide solution for 30 min, the ultrasonically soaked wood material was washed with deionized water, and the washed wood material was dried at 60°C for 24 h;

[0046] The activated wood material is subjected to carbonization treatment. Specifically, the temperature is raised to 700° C. at a heating rate of 5° C. / min, kept at this temperature for 3 hours, and naturally cooled to room temperature to obtain biomass carbon.

[0047] Step 2: Preparation of polydopamine-modified biomass carbon

[0048] Sequentially adding hydrochloric acid solution and dopamine hydrochloride to the tris(hydroxymethyl)aminomethane solution, wherein the concentration of the hydrochloric acid solution is 1 mol / L, the concentration of the tris(hydroxymethyl)aminomethane solution is 0.4 mol / L, and the molar ratio of the hydrochloric acid solution, the tris(hydroxymethyl)aminomethane solution and dopamine hydrochloride is 1:1.2:0.0316, and magnetically stirring at room temperature for 10 min to obtain a dopamine monomer solution;

[0049] The biomass carbon was soaked in a dopamine monomer solution, and a hydrogen peroxide solution was added to the dopamine monomer solution at a dropping speed of 0.02 ml / s, wherein the concentration of the hydrogen peroxide solution was 0.043 mol / L, and the volume ratio of the hydrogen peroxide solution to the dopamine monomer solution was 1:35. After the hydrogen peroxide solution was added, the biomass carbon was soaked for 24 hours, and the biomass carbon was turned over every 4 hours;

[0050] Step 3: Preparation of biomass carbon / silver composite electromagnetic shielding material

[0051] A silver ammonia solution is prepared by adding a 0.1 mol / L silver nitrate solution to a 5% wt ammonia solution at a volume ratio of 5:2, and the polydopamine-modified biomass carbon is immersed in the prepared silver ammonia solution. The pH value of the silver ammonia solution in which the polydopamine-modified biomass carbon is immersed is adjusted to 10 with a 0.1 mol / L citric acid solution, and a 0.2 mol / L glucose solution is added, the volume ratio of the glucose solution to the silver nitrate solution is 1:1, and an ultrasonic reaction is performed for 30 minutes. During the ultrasonic reaction, the polydopamine-modified biomass carbon is turned over every 5 minutes to obtain a biomass carbon / silver composite electromagnetic shielding material.

[0052] Example 2

[0053] Preparation of biomass carbon / silver composite electromagnetic shielding materials:

[0054] Step 1: Biomass carbon preparation

[0055] The wood material cut parallel to the wood growth direction was ultrasonically immersed in a 0.06 mol / L hexadecyltrimethylammonium bromide solution for 30 minutes, the ultrasonically immersed wood material was washed with deionized water, and the washed wood material was dried at 60°C for 24 hours;

[0056] The activated wood material is subjected to carbonization treatment. Specifically, the temperature is raised to 700° C. at a heating rate of 5° C. / min, kept at this temperature for 3 hours, and naturally cooled to room temperature to obtain biomass carbon.

[0057] Step 2: Preparation of polydopamine-modified biomass carbon

[0058] Sequentially adding hydrochloric acid solution and dopamine hydrochloride to the tris(hydroxymethyl)aminomethane solution, wherein the concentration of the hydrochloric acid solution is 1 mol / L, the concentration of the tris(hydroxymethyl)aminomethane solution is 0.4 mol / L, and the molar ratio of the hydrochloric acid solution, the tris(hydroxymethyl)aminomethane solution and dopamine hydrochloride is 1:1.2:0.0316, and magnetically stirring at room temperature for 10 min to obtain a dopamine monomer solution;

[0059] The biomass carbon was soaked in a dopamine monomer solution, and a hydrogen peroxide solution was added to the dopamine monomer solution at a dropping speed of 0.02 ml / s, wherein the concentration of the hydrogen peroxide solution was 0.043 mol / L, and the volume ratio of the hydrogen peroxide solution to the dopamine monomer solution was 1:35. After the hydrogen peroxide solution was added, the biomass carbon was soaked for 24 hours, and the biomass carbon was turned over every 4 hours;

[0060] Step 3: Preparation of biomass carbon / silver composite electromagnetic shielding material

[0061] A silver ammonia solution is prepared by adding a 0.1 mol / L silver nitrate solution to a 5% wt ammonia solution at a volume ratio of 5:2, and the polydopamine-modified biomass carbon is immersed in the prepared silver ammonia solution. The pH value of the silver ammonia solution in which the polydopamine-modified biomass carbon is immersed is adjusted to 10 with a 0.1 mol / L citric acid solution, and a 0.2 mol / L glucose solution is added, the volume ratio of the glucose solution to the silver nitrate solution is 1:1, and an ultrasonic reaction is performed for 30 minutes. During the ultrasonic reaction, the polydopamine-modified biomass carbon is turned over every 5 minutes to obtain a biomass carbon / silver composite electromagnetic shielding material.

[0062] Example 3

[0063] Preparation of biomass carbon / silver composite electromagnetic shielding materials:

[0064] Step 1: Biomass carbon preparation

[0065] The wood material cut perpendicular to the wood growth direction was ultrasonically soaked in a 0.1 mol / L hexadecyltrimethylammonium bromide solution for 30 minutes, the ultrasonically soaked wood material was washed with deionized water, and the washed wood material was dried at 60°C for 24 hours;

[0066] The activated wood material is subjected to carbonization treatment. Specifically, the temperature is raised to 800° C. at a heating rate of 5° C. / min, kept at this temperature for 3 hours, and naturally cooled to room temperature to obtain biomass carbon.

[0067] Step 2: Preparation of polydopamine-modified biomass carbon

[0068] Sequentially adding hydrochloric acid solution and dopamine hydrochloride to the tris(hydroxymethyl)aminomethane solution, wherein the concentration of the hydrochloric acid solution is 1 mol / L, the concentration of the tris(hydroxymethyl)aminomethane solution is 0.4 mol / L, and the molar ratio of the hydrochloric acid solution, the tris(hydroxymethyl)aminomethane solution and dopamine hydrochloride is 1:1.2:0.0316, and magnetically stirring at room temperature for 10 min to obtain a dopamine monomer solution;

[0069] The biomass carbon was soaked in a dopamine monomer solution, and a hydrogen peroxide solution was added to the dopamine monomer solution at a dropping speed of 0.02 ml / s, wherein the concentration of the hydrogen peroxide solution was 0.043 mol / L, and the volume ratio of the hydrogen peroxide solution to the dopamine monomer solution was 1:35. After the hydrogen peroxide solution was added, the biomass carbon was soaked for 24 hours, and the biomass carbon was turned over every 4 hours;

[0070] Step 3: Preparation of biomass carbon / silver composite electromagnetic shielding material

[0071] A silver ammonia solution is prepared by adding 0.1 mol / L silver nitrate solution to a 5% wt ammonia solution at a volume ratio of 5:2, and polydopamine-modified biomass carbon is immersed in the prepared silver ammonia solution. The pH value of the silver ammonia solution in which the polydopamine-modified biomass carbon is immersed is adjusted to 10 with a 0.1 mol / L citric acid solution, and 0.2 mol / L glucose solution is added, the volume ratio of the glucose solution to the silver nitrate solution is 1:1, and an ultrasonic reaction is performed for 60 minutes. During the ultrasonic reaction, the polydopamine-modified biomass carbon is turned over every 5 minutes to obtain a biomass carbon / silver composite electromagnetic shielding material.

[0072] Example 4

[0073] Preparation of biomass carbon / silver composite electromagnetic shielding materials:

[0074] Step 1: Biomass carbon preparation

[0075] The wood material cut parallel to the wood growth direction was ultrasonically soaked in a 0.1 mol / L hexadecyltrimethylammonium bromide solution for 30 minutes, the ultrasonically soaked wood material was washed with deionized water, and the washed wood material was dried at 60°C for 24 hours;

[0076] The activated wood material is subjected to carbonization treatment. Specifically, the temperature is raised to 800° C. at a heating rate of 5° C. / min, kept at this temperature for 3 hours, and naturally cooled to room temperature to obtain biomass carbon.

[0077] Step 2: Preparation of polydopamine-modified biomass carbon

[0078] Sequentially adding hydrochloric acid solution and dopamine hydrochloride to the tris(hydroxymethyl)aminomethane solution, wherein the concentration of the hydrochloric acid solution is 1 mol / L, the concentration of the tris(hydroxymethyl)aminomethane solution is 0.4 mol / L, and the molar ratio of the hydrochloric acid solution, the tris(hydroxymethyl)aminomethane solution and dopamine hydrochloride is 1:1.2:0.0316, and magnetically stirring at room temperature for 10 min to obtain a dopamine monomer solution;

[0079] The biomass carbon was soaked in a dopamine monomer solution, and a hydrogen peroxide solution was added to the dopamine monomer solution at a dropping speed of 0.02 ml / s, wherein the concentration of the hydrogen peroxide solution was 0.043 mol / L, and the volume ratio of the hydrogen peroxide solution to the dopamine monomer solution was 1:35. After the hydrogen peroxide solution was added, the biomass carbon was soaked for 24 hours, and the biomass carbon was turned over every 4 hours;

[0080] Step 3: Preparation of biomass carbon / silver composite electromagnetic shielding material

[0081] A silver ammonia solution is prepared by adding 0.1 mol / L silver nitrate solution to a 5% wt ammonia solution at a volume ratio of 5:2, and polydopamine-modified biomass carbon is immersed in the prepared silver ammonia solution. The pH value of the silver ammonia solution in which the polydopamine-modified biomass carbon is immersed is adjusted to 10 with a 0.1 mol / L citric acid solution, and 0.2 mol / L glucose solution is added, the volume ratio of the glucose solution to the silver nitrate solution is 1:1, and an ultrasonic reaction is performed for 60 minutes. During the ultrasonic reaction, the polydopamine-modified biomass carbon is turned over every 5 minutes to obtain a biomass carbon / silver composite electromagnetic shielding material.

[0082] Example 5

[0083] Preparation of biomass carbon / silver composite electromagnetic shielding materials:

[0084] Step 1: Biomass carbon preparation

[0085] The wood material cut perpendicular to the wood growth direction was ultrasonically soaked in a 0.06 mol / L hexadecyltrimethylammonium bromide solution for 30 minutes, the ultrasonically soaked wood material was washed with deionized water, and the washed wood material was dried at 60°C for 24 hours;

[0086] The activated wood material is subjected to carbonization treatment, specifically, the temperature is raised to 900°C at a heating rate of 5°C / min, kept at this temperature for 3 hours, and naturally cooled to room temperature to obtain biomass carbon;

[0087] Step 2: Preparation of polydopamine-modified biomass carbon

[0088] Sequentially adding hydrochloric acid solution and dopamine hydrochloride to the tris(hydroxymethyl)aminomethane solution, wherein the concentration of the hydrochloric acid solution is 1 mol / L, the concentration of the tris(hydroxymethyl)aminomethane solution is 0.4 mol / L, and the molar ratio of the hydrochloric acid solution, the tris(hydroxymethyl)aminomethane solution and dopamine hydrochloride is 1:1.2:0.0316, and magnetically stirring at room temperature for 10 min to obtain a dopamine monomer solution;

[0089] The biomass carbon was soaked in a dopamine monomer solution, and a hydrogen peroxide solution was added to the dopamine monomer solution at a dropping speed of 0.02 ml / s, wherein the concentration of the hydrogen peroxide solution was 0.043 mol / L, and the volume ratio of the hydrogen peroxide solution to the dopamine monomer solution was 1:35. After the hydrogen peroxide solution was added, the biomass carbon was soaked for 24 hours, and the biomass carbon was turned over every 4 hours;

[0090] Step 3: Preparation of biomass carbon / silver composite electromagnetic shielding material

[0091] A silver ammonia solution is prepared by adding 0.1 mol / L silver nitrate solution to a 5% wt ammonia solution at a volume ratio of 5:2, and polydopamine-modified biomass carbon is immersed in the prepared silver ammonia solution. The pH value of the silver ammonia solution in which the polydopamine-modified biomass carbon is immersed is adjusted to 10 with a 0.1 mol / L citric acid solution, and 0.2 mol / L glucose solution is added, the volume ratio of the glucose solution to the silver nitrate solution is 1:1, and an ultrasonic reaction is performed for 60 minutes. During the ultrasonic reaction, the polydopamine-modified biomass carbon is turned over every 5 minutes to obtain a biomass carbon / silver composite electromagnetic shielding material.

[0092] Example 6

[0093] Preparation of biomass carbon / silver composite electromagnetic shielding materials:

[0094] Step 1: Biomass carbon preparation

[0095] The wood material cut parallel to the wood growth direction was ultrasonically soaked in a 0.03 mol / L hexadecyltrimethylammonium bromide solution for 30 minutes, the ultrasonically soaked wood material was washed with deionized water, and the washed wood material was dried at 60°C for 24 hours;

[0096] The activated wood material is subjected to carbonization treatment, specifically, the temperature is raised to 900° C. at a heating rate of 5° C. / min, kept at this temperature for 3 hours, and naturally cooled to room temperature to obtain biomass carbon;

[0097] Step 2: Preparation of polydopamine-modified biomass carbon

[0098] Sequentially adding hydrochloric acid solution and dopamine hydrochloride to the tris(hydroxymethyl)aminomethane solution, wherein the concentration of the hydrochloric acid solution is 1 mol / L, the concentration of the tris(hydroxymethyl)aminomethane solution is 0.4 mol / L, and the molar ratio of the hydrochloric acid solution, the tris(hydroxymethyl)aminomethane solution and dopamine hydrochloride is 1:1.2:0.0316, and magnetically stirring at room temperature for 10 min to obtain a dopamine monomer solution;

[0099] The biomass carbon was soaked in a dopamine monomer solution, and a hydrogen peroxide solution was added to the dopamine monomer solution at a dropping speed of 0.02 ml / s, wherein the concentration of the hydrogen peroxide solution was 0.043 mol / L, and the volume ratio of the hydrogen peroxide solution to the dopamine monomer solution was 1:35. After the hydrogen peroxide solution was added, the biomass carbon was soaked for 24 hours, and the biomass carbon was turned over every 4 hours;

[0100] Step 3: Preparation of biomass carbon / silver composite electromagnetic shielding material

[0101] A silver ammonia solution is prepared by adding a 0.1 mol / L silver nitrate solution to a 5% wt ammonia solution at a volume ratio of 5:2, and the polydopamine-modified biomass carbon is immersed in the prepared silver ammonia solution. The pH value of the silver ammonia solution in which the polydopamine-modified biomass carbon is immersed is adjusted to 10 with a 0.1 mol / L citric acid solution, and a 0.2 mol / L glucose solution is added, the volume ratio of the glucose solution to the silver nitrate solution is 1:1, and an ultrasonic reaction is performed for 30 minutes. During the ultrasonic reaction, the polydopamine-modified biomass carbon is turned over every 5 minutes to obtain a biomass carbon / silver composite electromagnetic shielding material.

[0102] Example 7

[0103] The microscopic morphology of the cross-section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 1, Example 2, Example 3, Example 4, Example 5 and Example 6 was observed using a cold field emission scanning electron microscope of model Hitachi S4800. The acceleration voltage used was 5 kV. The scanning electron microscope photos of the cross-section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 1, Example 2, Example 3, Example 4, Example 5 and Example 6 are shown in FIG. Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6.

[0104] like Figure 1 As shown, in the cross section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 1, for the wood material cut perpendicular to the growth direction of the wood, silver particles are deposited along the wood fibers and are evenly distributed.

[0105] like Figure 2 As shown, in the cross-section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 2, for wood materials cut parallel to the growth direction of the wood, silver particles are deposited along the pores of the wood material, and the particles can enter the pores, thereby achieving effective combination between the biomass carbon and the silver particles.

[0106] like Figure 3 As shown, in the cross section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 3, for the wood material cut perpendicular to the wood growth direction, a large amount of silver particles are deposited along the wood fibers, the particles are closely distributed, and the silver particles can fully cover the wood cross section. As the deposition time increases, the silver particle content increases significantly.

[0107] like Figure 4 As shown, the cross-section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 4, for the wood material cut parallel to the growth direction of the wood, silver particles are deposited along the honeycomb porous structure of the wood material, forming a dense silver layer on the surface and inside of the wood channel, which can form a good conductive path.

[0108] like Figure 5 As shown, in the cross section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 5, for the wood material cut perpendicular to the growth direction of the wood, the silver particles are of uniform size and evenly distributed on the surface of the wood fibers, and the silver layer is dense.

[0109] like Figure 6 As shown, in the cross section of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 6, for the wood material cut parallel to the growth direction of the wood, the silver particles enter the porous channels, and the biomass carbon and the silver particles can be effectively combined.

[0110] The electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding materials prepared in Example 3, Example 4 and Example 5 was tested using a vector network analyzer of model N523OC PNA-L. The test method was a waveguide method. The tested bands were X-band (8-12 GHz) and Ka-band (26.5-40 GHz). The number of scanning points was 400. The electromagnetic shielding performance diagrams of the biomass carbon / silver composite electromagnetic shielding materials prepared in Example 3, Example 4 and Example 5 in the X-band are shown in order. Figure 7 , Figure 8 and Fig. 9The electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 3 and Example 4 in the Ka band is shown in FIG. Fig.10 and Fig.11 .

[0111] like Figure 7 As shown, the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 3 is 55.1-60dB in the X-band. Figure 3 As shown, it means that silver nanoparticles are successfully coated on the surface of biomass carbon, and the effective combination of the two can improve the electromagnetic shielding performance.

[0112] like Figure 8 As shown, the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 4 is 59.6-64.7dB in the X-band. Figure 4 As shown, since silver nanoparticles can be plated inside the channel to form multiple interfaces, electromagnetic waves are caused to undergo multiple reflections inside, thereby improving electromagnetic shielding performance and better realizing the synergistic effect between biomass carbon and conductive silver particles.

[0113] like Fig. 9 As shown, the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 5 is 56.7-62.5dB in the X-band. Figure 5 As shown, the silver particles are uniformly and densely deposited on the surface of the wood material, forming an excellent conductive network and achieving excellent electromagnetic shielding performance.

[0114] like Fig.10 As shown, the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 3 is 58.2-67.8dB in the Ka band, which is equivalent to the performance in the X band. It has excellent electromagnetic shielding capabilities in both the X band and the Ka band, and can simultaneously meet the application requirements of dual-band electromagnetic shielding materials.

[0115] like Fig.11 As shown, the electromagnetic shielding performance of the biomass carbon / silver composite electromagnetic shielding material prepared in Example 4 is 83.9-104.9dB in the Ka band, which is about 40dB higher than the performance in the X band. It has excellent electromagnetic shielding capabilities in both the X band and the Ka band, and can meet the application requirements of dual-band electromagnetic shielding materials at the same time.

[0116] The preparation method of the biomass carbon / silver composite electromagnetic shielding material and the material thereof of the present invention have the following beneficial effects:

[0117] 1. The wood material is activated by using hexadecyltrimethylammonium bromide solution before carbonization, so that more favorable functional group inheritance can be obtained before carbonization, avoiding the deficiency caused by the inertness of the surface of the material after carbonization, so that the surface of the biomass carbon material after carbonization is positively charged, and due to the electrostatic adsorption of the positive charge, the effective combination of the biomass carbon material and dopamine is promoted;

[0118] 2. The polydopamine layer is formed by adhering dopamine monomers to the cell channels of carbonized wood, and hydrogen peroxide is added during the formation process to reduce the time for forming the polydopamine layer, thereby ensuring that a polydopamine film layer with uniform thickness is obtained in a short time;

[0119] 3. By depositing silver nanoparticles on the surface and internal pores of biomass carbon modified with polydopamine, the wood material and the conductive silver particles are effectively combined. The vertically cut wood blocks carbonized at 800°C for 3 hours have an electromagnetic shielding performance of 59.6-64.7 dB in the X-band and 83.9-104.9 dB in the Ka-band. They have excellent electromagnetic shielding capabilities in both bands and can meet the application requirements of dual-band electromagnetic shielding materials at the same time. The shielding efficiency reaches 99.99%;

[0120] 4. The preparation method of the biomass carbon / silver composite electromagnetic shielding material of the present invention has the advantages of being safe, reliable and pollution-free. The prepared biomass carbon / silver composite electromagnetic shielding material has the characteristics of being anti-corrosive, moisture-proof, antibacterial and having efficient electromagnetic shielding performance, and is suitable for large-scale production.

[0121] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a biomass carbon / silver composite electromagnetic shielding material, characterized in that: The method comprises: Step 1: Biomass carbon preparation The wood material is activated by using a hexadecyltrimethylammonium bromide solution, and the activated wood material is carbonized to obtain biomass carbon; Step 2: Preparation of polydopamine-modified biomass carbon A dopamine monomer solution is prepared by using a hydrochloric acid solution, a tris(hydroxymethyl)aminomethane) solution and dopamine hydrochloride according to a ratio, and a hydrogen peroxide solution and the prepared dopamine monomer solution are used to modify the biomass carbon according to a ratio to obtain a polydopamine-modified biomass carbon; Step 3: Preparation of biomass carbon / silver composite electromagnetic shielding material Silver nitrate solution and ammonia solution are used to prepare a silver ammonia solution according to a ratio, and the polydopamine-modified biomass carbon is immersed in the prepared silver ammonia solution. After the pH value of the silver ammonia solution is adjusted, a glucose solution is added, and an ultrasonic reaction is performed to prepare a biomass carbon / silver composite electromagnetic shielding material; In step 1, a hexadecyltrimethylammonium bromide solution is used to perform an active treatment on the wood material, including: ultrasonically immersing the wood material in a hexadecyltrimethylammonium bromide solution with a concentration of 0.03-0.1 mol / L for 30 minutes, washing the ultrasonically immersed wood material with deionized water, and drying the washed wood material at a temperature of 60° C. for 24 hours; In step 2, a dopamine monomer solution is prepared by using a hydrochloric acid solution, a tris(hydroxymethyl)aminomethane solution and dopamine hydrochloride according to a ratio, including: adding a hydrochloric acid solution and dopamine hydrochloride to a tris(hydroxymethyl)aminomethane solution in sequence, wherein the concentration of the hydrochloric acid solution is 1 mol / L, the concentration of the tris(hydroxymethyl)aminomethane solution is 0.4 mol / L, and the molar ratio of the hydrochloric acid solution, the tris(hydroxymethyl)aminomethane solution and the dopamine hydrochloride is 1:1.2:0.0316, and magnetically stirring at room temperature for 10 minutes to obtain a dopamine monomer solution; In step 2, the biomass carbon is modified by using a hydrogen peroxide solution and a prepared dopamine monomer solution according to a ratio, including: soaking the biomass carbon in the dopamine monomer solution, and dripping the hydrogen peroxide solution into the dopamine monomer solution at a dripping speed of 0.02 ml / s, wherein the concentration of the hydrogen peroxide solution is 0.043 mol / L, and the volume ratio of the hydrogen peroxide solution to the dopamine monomer solution is 1:35; Step three, comprising: adding 0.1 mol / L silver nitrate solution to 5%wt ammonia solution at a volume ratio of 5:2 to prepare a silver ammonia solution, soaking the polydopamine-modified biomass carbon in the prepared silver ammonia solution, using 0.1 mol / L citric acid solution to adjust the pH value of the silver ammonia solution soaked with the polydopamine-modified biomass carbon to 10, adding 0.2 mol / L glucose solution, and ultrasonically reacting for 30-60 minutes to obtain a biomass carbon / silver composite electromagnetic shielding material; the volume ratio of the glucose solution to the silver nitrate solution is 1:

1.

2. The method for preparing the biomass carbon / silver composite electromagnetic shielding material according to claim 1, characterized in that: In step 1, the carbonization treatment includes: heating to 700-900°C at a heating rate of 5°C / min, keeping the temperature for 3 hours, and naturally cooling to room temperature.

3. The method for preparing the biomass carbon / silver composite electromagnetic shielding material according to claim 1, characterized in that: In step 2, after the hydrogen peroxide solution is added, the biomass carbon is soaked for 24 hours, and the biomass carbon is turned over every 4 hours.

4. The method for preparing the biomass carbon / silver composite electromagnetic shielding material according to claim 1, characterized in that: In step three, during the ultrasonic reaction, the polydopamine-modified biomass carbon is turned over every 5 minutes.

5. A biomass carbon / silver composite electromagnetic shielding material, characterized in that: The biomass carbon / silver composite electromagnetic shielding material is prepared according to any one of the methods described in claims 1-4.

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