阅读说明：本技术 一种制备电磁波吸收材料的方法 (Method for preparing electromagnetic wave absorbing material ) 是由 赵岩 李宗儒 石琼 文敏玥 万祥龙 李建军 刘银 于 2021-08-23 设计创作，主要内容包括：一种制备电磁波吸收材料的方法,包括S1、称取一定量的炼焦煤经过破碎、筛分,将筛得物放入烘箱,烘干后取出,得到样品煤；S2、按照一定比例称取一定量的样品煤,木质素,氢氧化钾,再加入适量去离子水,充分搅拌均匀,放入干燥箱中烘干成固体；S3、取出S2中获得的固体放入瓷舟,再将其放入管式炉,通入氮气,以一定升温速率逐渐升温至目标温度,在该目标温度下煅烧保温一段时候后降温至常温,取出瓷舟中的样品。S4、向S3所得样品中加入一定量的水,在加入一定量的盐酸进行抽滤,烘干得到电磁波吸收材料。该电磁波吸收材料制备方法简单,材料性能突出,具有广阔的市场应用前景。(A method for preparing electromagnetic wave absorbing material comprises S1, weighing a certain amount of coking coal, crushing and screening, putting the screened material into an oven, drying and taking out to obtain sample coal; s2, weighing a certain amount of sample coal, lignin and potassium hydroxide according to a certain proportion, adding a proper amount of deionized water, fully and uniformly stirring, and putting into a drying oven to be dried into a solid; s3, taking out the solid obtained in the S2, putting the solid into a porcelain boat, putting the porcelain boat into a tube furnace, introducing nitrogen, gradually heating to a target temperature at a certain heating rate, calcining at the target temperature, keeping the temperature for a period of time, cooling to the normal temperature, and taking out a sample in the porcelain boat. And S4, adding a certain amount of water into the sample obtained in the step S3, adding a certain amount of hydrochloric acid, performing suction filtration, and drying to obtain the electromagnetic wave absorbing material. The electromagnetic wave absorption material has the advantages of simple preparation method, outstanding material performance and wide market application prospect.)

1. A method of producing an electromagnetic wave absorbing material, comprising the steps of:

s1, weighing a certain amount of coking coal, crushing and screening, putting the screened material into an oven, drying and taking out to obtain sample coal;

s2, weighing a certain amount of sample coal, lignin and potassium hydroxide according to a certain proportion, adding a proper amount of deionized water, fully and uniformly stirring, and putting into a drying oven to be dried into a solid;

s3, taking out the solid obtained in the S2, putting the solid into a porcelain boat, putting the porcelain boat into a tube furnace, introducing nitrogen, gradually heating to a target temperature at a certain heating rate, calcining at the target temperature, keeping the temperature for a period of time, cooling to the normal temperature, and taking out a sample in the porcelain boat;

and S4, adding a certain amount of water into the sample obtained in the step S3, adding a certain amount of hydrochloric acid, performing suction filtration, and drying to obtain the electromagnetic wave absorbing material.

2. The method of claim 1, wherein the coking coal is crushed in step S1 by planetary ball milling pretreatment at 350rpm for 30min forward rotation and 30min reverse rotation, and the forward rotation and the reverse rotation are alternately performed for 2-4 h.

3. The method of claim 1, wherein: the temperature of the oven in the step S1 is 105 ℃, and the drying time is 1.5-2 h.

4. The method as claimed in claim 1, wherein the mass ratio of the sample coal, the lignin and the potassium hydroxide in the step S2 is (0.1-6): (0.1-6): (0.1-6).

5. The method as claimed in claim 1, wherein the temperature raising rate in step S3 is 5 ℃/min, the calcination temperature is 400-800 ℃, and the holding time is 30-60 min.

6. The method according to claim 1, wherein the nitrogen flow rate is 60-80 ml/min.

7. The method according to claim 6, wherein the nitrogen flow rate is 70 ml/min.

8. The method of claim 1, wherein the step of adding hydrochloric acid to the solution in S4 to neutrality is followed by suction filtration and deionized water washing 3-5 times.

Technical Field

The invention belongs to the field of material chemistry, and particularly relates to a method for preparing an electromagnetic wave absorption material.

Background

Due to the increasing severity of greenhouse effect, people pay more attention to the development and utilization of clean, efficient and renewable energy sources, and biomass and coal co-combustion is considered to be one of the energy utilization modes for effectively controlling global warming. The biomass and coal mixed combustion not only can well utilize the biomass energy, but also can solve the problems of environmental problems and energy attenuation caused by coal combustion; the mixed combustion of biomass and coal is a relatively new research field, and some scholars at home and abroad have carried out research and analysis on mixed pyrolysis of biomass and coal and mixed combustion characteristics.

The coal mainly comprises five elements of carbon, hydrogen, oxygen, nitrogen and sulfur, the carbon content of the coal is high, and the carbon content of most of the coal is 75-95%. Coal is a widely used carbon source for activated carbon due to the high fixed carbon content. Coal is widely distributed in the earth crust and contains a large number of oxygen-containing functional groups, which can provide dipole polarization and promote microwave absorption. The coal has wide application, mainly comprises the application in three aspects of metallurgy, chemical industry and coal for power, and has the functions of mainly being used for combustion, gasification, coking and the like. Coal-based carbon can be used not only as an electrode for a supercapacitor, but also as an absorbent to remove organic contaminants such as malachite green and methylene blue. In addition, the traditional uses of coal, including power generation and coking, can cause severe environmental damage. Therefore, a new strategy for realizing high-value-added utilization of coal is urgently needed. Compared with fossil fuels, the unfavorable characteristics of low calorific value, high volatile content, high transportation cost and the like of biomass lignin limit the utilization of the biomass lignin as a renewable energy production raw material. However, the co-processing (i.e. pyrolysis, liquefaction, gasification, combustion) of woody biomass with coal is one of the most promising options to address these drawbacks arising in biomass utilization. This synergistic treatment both eliminates the disadvantages of biomass and coal and increases their advantages. The coal and biomass co-pyrolysis process can produce coke, tar, and gas. Due to the synergistic effect of co-pyrolysis of coal and biomass, research in this field has been receiving more and more attention in recent years.

The invention relates to a method for preparing an electromagnetic wave absorption material based on coal and lignin co-production, which prepares a coal and lignin derived functional material by co-processing coal and lignin and then calcining at high temperature. The prepared material has excellent electromagnetic wave absorption performance. Has important significance for reducing the harm of electromagnetic waves in the environment and expanding the derived application of coal and biomass.

Disclosure of Invention

In order to solve the above technical problems, an object of the present invention is to provide a method for preparing an electromagnetic wave absorbing material by co-processing coal and lignin. The method provides a solution for the utilization of biomass resources, the expansion of coal application and the reduction of electromagnetic wave harm.

In order to realize the purpose of the invention, the invention adopts the following technical scheme:

the invention aims to provide a method for preparing an electromagnetic wave absorbing material by co-processing coal and lignin, which comprises the following steps:

s1, weighing a certain amount of coking coal, crushing and screening, putting the screened material into an oven, drying and taking out to obtain sample coal;

s2, weighing a certain amount of sample coal, lignin and potassium hydroxide according to a certain proportion, adding a proper amount of deionized water, fully and uniformly stirring, and putting into a drying oven to be dried into a solid;

s3, taking out the solid obtained in the S2, putting the solid into a porcelain boat, putting the porcelain boat into a tube furnace, introducing nitrogen, gradually heating to a target temperature at a certain heating rate, calcining at the target temperature, keeping the temperature for a period of time, cooling to the normal temperature, and taking out a sample in the porcelain boat.

And S4, adding a certain amount of water into the sample obtained in the step S3, adding a certain amount of hydrochloric acid, performing suction filtration, and drying to obtain the electromagnetic wave absorbing material.

According to a further technical scheme, in the step S1, the coking coal is subjected to crushing treatment by adopting planetary ball milling pretreatment, the rotating speed of the planetary ball mill is 350rpm, forward rotation is carried out for 30min, reverse rotation is carried out for 30min, and then forward rotation and reverse rotation are alternately carried out for 4 h.

In the further technical scheme, the temperature of the oven in the step S1 is 105 ℃, and the drying time is 1.5-2 h.

In the step S2, the mass ratio of the sample coal, the lignin and the potassium hydroxide is (0.1-6): (0.1-6): 0.1-6).

In the further technical scheme, the temperature rise rate in the step S3 is 5 ℃/min, the calcination temperature is 400-800 ℃ respectively, and the heat preservation time is 30-60 min.

In a further technical scheme, the flow rate of the nitrogen is 60-80 ml/min.

According to a further technical scheme, hydrochloric acid is added into the S4 to be neutral, then suction filtration is carried out, and deionized water is used for washing for 3-5 times.

The invention has the beneficial effects that:

(1) by the method, the coal and the lignin are co-processed to obtain the novel electromagnetic wave absorbing material. The electromagnetic wave absorbing material is prepared by co-processing the coal and the lignin, so that the application range of the coal is expanded, a new way for utilizing biomass resources is developed, and the method has very important significance for fully utilizing the coal and the biomass resources.

(2) The preparation method is simple and is prepared by one-step calcination after pretreatment.

(3) The material prepared by the invention has good wave-absorbing performance on electromagnetic waves in a 2-18GHz wave band, and the optimal absorption can reach-51.89 dB.

(4) The material prepared by the invention is a carbon material, and has the advantages of low density and portability.

Drawings

Fig. 1 is an SEM spectrum of lignin.

FIG. 2 is an SEM spectrum of sample coal.

Fig. 3 is an SEM spectrum of the prepared electromagnetic wave absorbing material.

FIG. 4 is a graph showing the electromagnetic wave absorption properties of sample coals.

FIG. 5 is a graph showing electromagnetic wave absorption properties of lignin.

Fig. 6 is a graph of the electromagnetic wave absorption performance of the electromagnetic wave absorption material S0 prepared.

Fig. 7 is a graph of the electromagnetic wave absorption performance of the electromagnetic wave absorption material S1 prepared.

Fig. 8 is a graph of the electromagnetic wave absorption performance of the electromagnetic wave absorption material S2 prepared.

Detailed Description

The process of the present invention is illustrated below by means of specific examples, but the present invention is not limited thereto.

The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.

The lignin used in the following examples was purchased from Zhonggii recycling economy, Inc., and the coal was coking coal. Before use, the coal needs to be crushed by a planetary ball mill, then is sieved, and the sieved material is put into an oven to be dried for 2 hours at the temperature of 105 ℃ to obtain the required sample coal. The following examples were all conducted in a tube furnace with nitrogen gas being passed to provide an oxygen-free atmosphere at a flow rate of 60-80 ml/min. During the experiment: the coal and lignin were placed in the tube furnace intermediate section.

Example 1 coking coal calcination

Taking 6g of sample coal, adding 3g of KOH and 40ml of water, fully mixing at room temperature, putting the mixture into a porcelain boat after being dried in an oven, putting the porcelain boat into a tube furnace, heating to 600 ℃ at the heating rate of 5 ℃/s, preserving the heat for 60min, and taking the porcelain boat out after the temperature is reduced to the room temperature. And absorbing the solid product to be neutral by using a hydrochloric acid solution, and then putting the solid product into an oven for drying.

Example 2 Co-treatment calcination of coking coal and Lignin

This example operates the same as example 1, with the following different conditions: in this example, 5g of coking coal was weighed, 1g of lignin was weighed, and the lignin was directly mixed with the coking coal in KOH solution without any treatment.

Example 3 Co-treatment calcination of coking coal and Lignin

This example operates the same as example 1, with the following different conditions: in the example, 4g of coking coal is weighed, 2g of lignin is weighed, and the lignin is directly mixed with the coking coal in a KOH solution without any treatment.

Example 4 Co-treatment calcination of coking coal and Lignin

This example operates the same as example 1, with the following different conditions: in this example, 3g of coking coal was weighed, 3g of lignin was weighed, and the lignin was directly mixed with the coking coal in KOH solution without any treatment. The electromagnetic wave absorbing material prepared in this example was denoted as S1.

Example 5 Co-treatment calcination of coking coal and Lignin

This example operates the same as example 1, with the following different conditions: in the example, 2g of coking coal and 4g of lignin are weighed, and the lignin is directly mixed with the coking coal in a KOH solution without any treatment.

Example 6 Co-treatment calcination of coking coal and Lignin

This example operates the same as example 1, with the following different conditions: in this example, 1g of coking coal was weighed, 5g of lignin was weighed, and the lignin was directly mixed with the coking coal in KOH solution without any treatment.

Example 7 Lignin calcination

This example operates the same as example 1, with the following different conditions: in the example, coking coal was not weighed, lignin was weighed 6g, and lignin was mixed directly with coking coal in KOH solution without any treatment.

Example 8 Co-treatment calcination of coking coal and Lignin

This example operates the same as example 4, with the following different conditions: the temperature in this example was 400 ℃. The electromagnetic wave absorbing material prepared in this example was denoted as S0.

Example 9 Co-treatment calcination of coking coal and Lignin

This example operates the same as example 4, with the following different conditions: the temperature in this example was 800 ℃. The electromagnetic wave absorbing material prepared in this example was denoted as S2.

Referring to the accompanying drawings, fig. 1 to 3 are SEM spectrograms of lignin, sample coal and the prepared electromagnetic wave absorbing material, respectively. As can be seen from the 50 μm spectrum in fig. 1, the lignin is packed together by a number of round and spherical solid particles. As can be seen from the 10 μm spectrum in fig. 1, the lignin surface has rugged and wavy structure, and the small particles on the surface are probably caused by the presence of metal sodium ions in the alkali lignin. Figure 2 shows SEM images of coal at different magnifications. As can be seen from the spectra of 50 microns and 1 micron in fig. 1, the surface of the raw coal was irregular and the wrinkles were more pronounced. As can be seen from the spectra of 50 μm and 1 μm in fig. 3, the S1 surface of the prepared electromagnetic wave absorbing material has pores with different sizes, probably because the coal contains a large number of closed pores which may be partially converted into effective pores to reach the particle surface as the reaction proceeds. The holes are the basis for the material to have excellent electromagnetic wave absorption performance.

Referring to FIGS. 4-5, there are plots of electromagnetic wave absorption properties of sample coal and lignin, respectively. The thickness d corresponding to the optimal reflectivity peak value RL in the sample coal and lignin samples is relatively large, which can not meet the requirement of thin thickness of the wave-absorbing material. Furthermore, the electromagnetic wave absorption of coal does not satisfy the quarter-wave attenuation law, which is related to the presence of interference cancellation effects in the material. Having a strong resonance effect in a certain frequency range, which contributes more to the reflection loss, it is not obvious that the absorption peak frequency shifts to a lower frequency with increasing thickness. As can be seen from FIG. 4, the optimal reflectance peak RL for the sample coal is-15.98 dB, the corresponding peak intensity frequency is 6.48 GHz, and the thickness d =4.5 mm. As can be seen from fig. 5, the optimum reflectance peak RL for the sample lignin is-15.92 dB, corresponding to a peak intensity frequency of 5.76 GHz, and a thickness d =5.0 mm. The wave-absorbing material is required to have good electromagnetic wave absorption effect, light weight, wide absorption frequency, thin thickness and wide application range. Therefore, it can be seen that the electromagnetic wave absorption performance of simple coal and lignin does not meet the requirement of an excellent wave absorbing material.

Referring to fig. 6 to 8, electromagnetic wave absorption performance graphs of S0, S1, and S2 are shown. As can be seen from fig. 6, the optimum reflectance peak RL of sample S0 is-20.66 dB, corresponding to a peak intensity frequency of 17.44 GHz, and a thickness d =5.0 mm. As can be seen from fig. 7, the optimum reflectance peak RL of sample S1 is-51.89 dB, corresponding to a peak intensity frequency of 6.24 GHz, a thickness d =4.14 mm, and a bandwidth of 2.64 GHz. As can be seen from fig. 8, the optimum reflectance peak RL of sample S2 is-22.32 dB, corresponding to a peak intensity frequency of 14.4 GHz, a thickness d =4.0 mm, and a bandwidth of 1.36 GHz. Compared with S0 and S2, the RL value of the sample S1 is the best, the bandwidth is the largest, and the wave absorbing performance of S1 is better than that of pure coal and lignin. As can be seen from fig. 5-6, the RL value of S1 shifts to a low frequency with increasing thickness, which can be explained by quarter-wave attenuation and will not be described herein. As can be seen from the attached figures 4 to 8, compared with the method that only lignin and sample coal are adopted, the electromagnetic wave absorbing material prepared by the method has very good technical parameters, the optimal absorption can reach-51.89 dB, and the method shows that the method has great commercial value in the field of electromagnetic wave absorbing materials.

The present invention is not limited to the above-described embodiments, which are merely illustrative of the present invention and are not to be construed as limiting the present invention.